Showing papers on "QRS complex published in 1981"
TL;DR: Advanced signal processing of the ECG accurately identified the patients in the study with VT after myocardial infarction.
Abstract: Small, high-frequency electrocardiographic signals were recorded from the body surface in 39 patients with and 27 patients without ventricular tachycardia (VT). All patients were in normal sinus rhythm, had a previous myocardial infarction, were not taking antiarrhythmic drugs, and did not have bundle branch block. Bipolar X, Y, Z leads were signal averaged and processed by a bidirectional digital filter that allowed low-amplitude signals to be detected in the terminal QRS complex and ST segment. The high-pass filter frequency was 25 Hz. Patients with VT had a lower amplitude of high-frequency signal in the late QRS complex. In the last 40 msec of the filtered QRS complex, the patients with VT had 14.9 +/- 14.4 microV of high-frequency signal; patients without VT had 73.8 +/- 47.7 microV (p less than 0.0001). Ninety-two percent of the patients with VT had less than 25 microV of high-frequency voltage; only 7% of patients without VT had less than 25 microV (p less than 0.0001). Patients with VT had a longer QRS duration than those without VT, 139 +/- 26 vs 95 +/- 10 msec (p less than 0.0001). The QRS duration was longer than 120 msec in 72% of the patients with VT but in none of the patients without VT (p less than 0.0001). In all patients there was no separate and discrete high-frequency signal in the ST segment. Advanced signal processing of the ECG accurately identified the patients in the study with VT after myocardial infarction.
1,136 citations
TL;DR: It is concluded that late potentials which represent late depolarization of a mass of ventricular tissue after slow conduction, herald increased susceptibility to ventricular tachyardia mainly in patients with ventricular aneurysms.
Abstract: Late potentials occurring after the QRS complex were searched for from the body surface using high-gain amplification and signal averaging techniques with filler sellings between 100 and 300 Hz at a sampling rate of 10 kHz. The number of repetitions of the averaging process ranged between 150 and 300 Hz.
Sixty-seven patients were studied. In 11 control subjects, no late potentials were delected within the ST segment. Late potentials were observed in 3/27 patients without previously documented ventricular tachycardia all having left ventricular aneurysms. All three patients had evidence of increased ventri-l cular vulnerability (one dying from ventricular tachycardia; one with stimulus-inducible ventricular tachy–cardia; one with multiple episodes of ventricular fibrillation after surgery). In patients with previously k documented ventricular tachycardia and/or fibrillation, late potentials occurred in 7/14 cases (50%), mainly in those with aneurysms (6/8 patients = 7596/ In another 15 patients with ventricular tachycardia and/or fibrillation who were on an effective long-term antiarrhylhmic regimen no late potentials were found. Mean onset of late potentials after the QRS complex was 38 ± 20.1 ms, mean amplitude was 3.9 ± 2.0 uv, and mean duration was 17.1 ± 5.4 ms.
We conclude that late potentials which represent late depolarization of a mass of ventricular tissue after slow conduction, herald increased susceptibility to ventricular tachyardia mainly in patients with ventricular aneurysms.
270 citations
TL;DR: Delayed wave-form activity (D wave) extended a mean of 70 msec beyond the termination of the QRS complex and may represent persistence of the cardiac impulse in islands of myocardium and may be a manifestation of the delayed and fractionated activity, noted by previous investigators.
Abstract: In eight patients with chronic ventricular tachycardia and left ventricular aneurysms, we detected delayed ECG wave forms after the QRS complex from the body surface using a high-resolution ECG recorder, amplification and signal averaging. Delayed wave-form activity (D wave) extended a mean of 70 msec beyond the termination of th QRS complex. This delayed activity frequently extended to the limit of the recording window, and may thus continue throughout much of diastole. Antiarrhythmic agents never abolished the delayed activity; however, it was abolished by aneurysmectomy in four patients. Ventricular tachycardia did not recur after surgery in the four patients during a mean follow-up of 1 year. The D wave was not found in eight control patients who had chronic recurrent ventricular tachycardia nor in 11 of 12 who had aneurysms alone. The surface D wave can be readily and reproducibly detected by high-resolution electrocardiography and appears to be specific for patients with left ventricular aneurysms who also have chronic recurrent ventricular tachycardia. This delayed wave-form activity has been noted during catheter and surgical endocardial and epicardial mapping. It may represent persistence of the cardiac impulse in islands of myocardium and may be a manifestation of the delayed and fractionated activity, noted by previous investigators.
266 citations
TL;DR: It is concluded that MI increases low-amplitude QRS notching but diminishes total high-frequency voltage, probably because of an overall decrease in electromotive potentials and slowing of ventricular conduction.
Abstract: Studies have shown that the number of high-frequency QRS notches increases after myocardial infarction (MI). To assess overall high-frequency (greater than 80 Hz) potentials more quantitatively, we adapted filtered and the root-mean-square (RMS) voltage of the residual (80-300 Hz) signal computed. High-frequency RMS values were significantly (p less than 0.01) greater in leads II, III and aVf in normal subjects (n = 12) than in patients with inferior infarction (n = 12). Similarly, high-frequency RMS values were higher (p less than 0.01) in leads V2 and V5 in normal subjects (n = 14) than in patients with prior anterior MI (n = 14). A reduction in high-frequency RMS values with inferior infarction was independently confirmed using Fourier analysis of the QRS in lead II. QRS notching in these subjects was also quantified by computing the number of baseline crossings of the first derivative (dV/dt). As predicted, notching was significantly greater (p less than 0.05) both with inferior MI (lead II) and anterior MI (lead V5). However, contrary to classic theory, the number of notches correlated negatively with direct measurements of high-frequency RMS voltage in lead II (r = -0.63) and lead V5 (r = -0.49). Positive correlations were obtained between high-frequency potentials and two new indexes that measure the amplitude of QRS dV/dt-peak-to-peak amplitude of dV/dt and RMS dV/dt. Using these indexes, absolute separation of inferior MI patients and normal subjects was obtained. We conclude that MI increases low-amplitude QRS notching but diminishes total high-frequency voltage, probably because of an overall decrease in electromotive potentials and slowing of ventricular conduction.
141 citations
TL;DR: It is demonstrated that microvolt-level potentials arising from delayed ventricular activation can be reliably detected on the body surface, even when they occur just after the QRS complex.
Abstract: This study describes a noninvasive method for detecting delayed ventricular activation, caused by ischemia, on the body surface. Signal averaging and a newly developed high-pass digital filter were used. The filter has the property that it does not create an artifact or ring after the QRS complex ends, thereby allowing the detection of microvolt-level potentials that occur immediately after the QRS complex. Eleven dogs were studied before and during acute ischemia induced by coronary artery ligation and latex embolization. The ischemic region was mapped with bipolar electrodes and, after the chest was rapidly closed, signal-averaged recordings were made from the body surface. Repeated cycles of ventricular mapping and signal averaging were performed. In each dog, delayed and fractionated electrograms were recorded directly from the ischemic epicardium that lasted a maximum of 118 +/- 18 ms after QRS onset. The duration of the ventricular electrograms varied with time. Whenever delayed epicardial electrograms were recorded, filtered signal-averaged leads showed microvolt-level potentials early in the S-T segment that were continuous with the QRS complex. The duration of ventricular activation, as measured from the bipolar electrograms and from the filtered signal-averaged leads, correlated well (r = 0.93, P less than 0.001). Because of the absence of filter ringing, low-level potentials could be detected less than 40 ms after the QRS complex ended. This study demonstrates that microvolt-level potentials arising from delayed ventricular activation can be reliably detected on the body surface, even when they occur just after the QRS complex.
141 citations
TL;DR: A modified quadripolar electrode catheter provided for a stable model of complete AV block and is suitable for experiments in which heart rate control is required and may be of value for patients with tachycardia requiring His bundle section.
Abstract: A modified quadripolar electrode catheter that had two-thirds of the distal surface insulated with high-voltage plastic was inserted in 10 dogs. After a His bundle potential had been recorded, a synchronized direct-current electrical discharge was delivered between the electrodes showing the largest His bundle deflection using a standard direct-current defibrillator, and a metallic plate was positioned over the dog's back. Complete atrioventricular (AV) block was induced in 9 of 10 dogs, which were followed for 3 mo before being killed. During AV block, the QRS complex was broad and not preceded by a His bundle deflection. The mean control cycle length during AV block was 1,441 +/- 223 ms and decreased to 1,151 +/- 181 ms after exercise, a response that was usually abolished by beta-blockade. Overdrive pacing resulted in pacemaker suppression with gradual rate stabilization after 10-20 beats. There was no evidence of myocardial or valvular damage. This technique provides for a stable model of complete AV block and is suitable for experiments in which heart rate control is required. In addition, this technique may be of value for patients with tachycardia requiring His bundle section.
136 citations
TL;DR: The data suggest that torsades de pointes in this setting may be a rapid reentrant ventricular tachycardia closely related to recurrent sustained ventricular gyrations and a precursor to ventricular fibrillation and sudden death.
Abstract: Electrophysiologic studies were performed in 21 patients who had torsades de pointes. This ventricular tachyarrhythmia, characterized by rapid (200-250 beats/min) and irregular paroxysms and progressively varying QRS amplitude and polarity, occurred in the absence of electrolyte disturbance, antiarrhythmic drug therapy or acute ischemia. The QTc interval was prolonged in seven of 21 patients. Electrophysiologic study included ventricular pacing with the introduction of one to three extrastimuli and rapid ventricular pacing. The effect of i.v. procainamide or quinidine in these patients was also studied. Torsades de pointes was inducible n 19 of 21 patients. Induced episodes closely resembled spontaneous episodes. Torsades de pointes spontaneously progressed to ventricular tachycardia with a uniform morphology in three patients and to ventricular fibrillation in four. In eight patients, procainamide or quinidine converted torsades de pointes into typical reentrant ventricular tachycardia. Our data suggest that torsades de pointes in this setting may be a rapid reentrant ventricular tachycardia closely related to recurrent sustained ventricular tachycardia and a precursor to ventricular fibrillation and sudden death.
129 citations
TL;DR: It is concluded that when utilizing rapid ventricular pacing to interrupt ventricular tachycardia, a critical pacing rate may be required before interruption is achieved.
Abstract: The effects on spontaneously occurring ventricular tachycardia of rapidly pacing the right ventricle at rates faster than the rate of the ventricular tachycardia were studied during 10 episodes in seven patients. In three episodes, ventricular pacing interrupted the ventricular tachycardia at the initial pacing rate (111%, 114%, and 119% of the ventricular tachycardia rate, respectively). In seven episodes, the initial pacing rate failed to interrupt the ventricular tachycardia. In six of those seven episodes, the ventricular tachycardia was transiently entrained to the faster pacing rates. In one of those seven episodes, transient entrainment of the ventricular tachycardia could not be distinguished from over-drive suppression. In all seven episodes, the tachycardia was later interrupted by pacing at more rapid rates. The successful pacing rate ranged from 111-141% (mean 125%) of the spontaneous ventricular tachycardia rate. It is concluded that when utilizing rapid ventricular pacing to interrupt ventricular tachycardia, a critical pacing rate may be required before interruption is achieved. Pacing at rates slower than the critical rate but faster than the spontaneous ventricular tachycardia rate may only transiently entrain the ventricular tachycardia to the pacing rate without interrupting it. During the period of transient entrainment, fusion QRS complexes are likely to be present.
129 citations
01 Jan 1981
TL;DR: The correct diagnosis of the site of origin of a regular tachycardia with a wide QRS (≥0.12 s) complex continues to be an exciting challenge.
Abstract: The correct diagnosis of the site of origin of a regular tachycardia with a wide QRS (≥0.12 s) complex continues to be an exciting challenge. It is not only an exercise in electrocardiography, but also a decision with important therapeutic and prognostic consequences.
70 citations
TL;DR: A single catheter designed for P synchronous pacing empJoying circumferentially placed atrial sensing electrodes has demonstrated unique atrial sensed voltages with excellent QRS signal rejection.
Abstract: P synchronous pacing has long been identified as advantageous for patients with atrioveniricular conduction defects and intact sinus node function. Prior endocavitury systems have been infrequently employed, because of unreliable P wave sensing from standard ring electrodes in the atrium or the requirement for a second atriaJ sensing lead. A single endocardial lead employing a unipolar ventricular stimulating electrode and an orthogonal P wave sensing design was developed and tested in 22 patients undergoing electrophysiologic study or pacemaker implantation. Thirteen centimeters from the stimulating tip of a standard permanent pacing lead, three or four electrodes with a surface area of one millimeter squared, equidistant from the tip, were placed circumferentially about the catheter. With the catheter tip normally placed in the right ventricular apex, atrial sensing eJectrodes were positioned in the mid-high lateral right atrium, adjacent to, but not affixed to, the right atrial wall. Bipolar orthogonal leads X and Y were obtained. In 22 patients, during sinus rhythm, atrial electrogram voltages in the X axis of 2.47 plus or minus 1.6 millivolts and 2.32 plus or minus 1.6 millivolts in the Y axis were recorded. QRS voltages of 0.078 millivolts and 0.073 millivolts, respectively, allowed dramatic ability to discriminate P from QRS complexes (P/QRS equals 32/1). There was no change in QRS voltages recorded during spontaneous premature ventricular contractions, bipolar or unipolar ventricular pacing. A single catheter designed for P synchronous pacing empJoying circumferentially placed atrial sensing electrodes has demonstrated unique atrial sensing voltages with excellent QRS signal rejection. (PACE, Vol. 4, November-December, 1981)
55 citations
TL;DR: To examine electrocardiographic changes with aging in the same persons, serial recordings were taken in 440 healthy male participants of the Normative Aging Study, finding some previously described cross-sectional age differences truly represent longitudinal age trends in electrocardsiographic patterns.
Abstract: Previous cross-sectional population studies have shown age differences In electrocardiographic wave patterns, including lower wave amplitudes and a leftward shift of the frontal plane axis in older people. However, cross-sectional results may be due to cohort differences and the data imply only that these changes actually occur in persons as they age. In order to examine electrocardiographic changes with aging in the same persons, serial recordings, obtained 10 years apart, were taken in 440 healthy male participants of the Normative Aging Study, who were 23 to 66 years old on their first examination. At examination 1, R and S wave amplitudes were smaller and frontal plane axis measurements were shifted to the left in older men. Longitudinal changes in these same variables were consistent with the cross-sectional results. In addition, the P-R and Q-T interval durations were longer, the QRS duration was shorter and the T wave amplitude was smaller at the second examination. The longitudinal rate of change of S wave amplitude varied among age groups, decreasing more in younger men. Thus, some previously described cross-sectional age differences truly represent longitudinal age trends in electrocardiographic patterns.
TL;DR: The electrocardiogram has an extremely limited value in population screening below the age of 50 and a strong association between total mortality and major ST depression and T wave abnormalities in both sexes is found.
Abstract: In the Copenhagen City Heart Study 9348 men and 10 314 women, aged 20 or more, were examined. A resting 12 lead electrocardiogram was recorded in each subject. The prevalence of all electrocardiographic signs with the exception of axis deviation, high amplitude R wave, minor T wave abnormality, prolonged and short P(Q)R interval was very low below the age of 40 in men and below the age of 50 in women. Rates for Q-QS abnormalities, left axis deviation, ST depression and T wave abnormalities, premature beats, and atrial fibrillation increased with age, and the prevalence was higher for men than for women. In comparison with other European studies, the prevalence of major and minor electrocardiographic abnormalities of our study is high, similar to those found in Finland.
We found a strong association between total mortality and major ST depression and T wave abnormalities in both sexes. A similar strong correlation was observed between mortality and Q-QS and LBBB in men.
In conclusion, the electrocardiogram has an extremely limited value in population screening below the age of 50. The well-known correlation between electrocardiographic signs and ischaemic heart disease mortality was confirmed by our data in relation to total mortality.
TL;DR: It is postulated that in these patients a slow atrioventricular (A-V) nodal pathway is used in the retrograde direction during echoes showing a shorter P-R than R-P interval, which favors incorporation of an accessory pathway with slow retrograde conduction in the tachycardia circuit.
Abstract: Single test stimulation of the ventricle revealed initiation of echoes with a supraventricular QRS complex with a shorter P-R than R-P interval in 28 of 300 patients consecutively studied with programmed electrical stimulation of the heart because of documented or suspected tachycardias. In all 28 the initiation of echoes was related to a discontinuity in the retrograde conduction curve. In 10 patients a different atrial activation sequence in the endocavitary leads was present before and after the discontinuity in the retrograde conduction curve. In five of these a sustained tachycardia with a shorter P-R than R-P interval could be initiated, and in all five patients an accessory pathway with a long conduction time as the retrograde arm of the tachycardia circuit could be demonstrated. In these five patients spontaneous initiation of tachycardia was observed during sinus rhythm or after atrial premature beats. Tachycardia accelerated after the administration of atropine. In the remaining 23 patients the initiation of echoes showing a shorter P-R than R-P interval was nonsustained. In these patients spontaneous initiation of such echoes during sinus rhythm or initiation by atrial premature beats was not observed, and echoes with this relation of the P-R and R-P intervals systematically disappeared after administration of atropine. It is postulated that in these patients a slow atrioventricular (A-V) nodal pathway is used in the retrograde direction during echoes showing a shorter P-R than R-P interval. Sustained A-V junctional tachycardia showing this relation between P-R and R-P intervals favors incorporation of an accessory pathway with slow retrograde conduction in the tachycardia circuit.
TL;DR: Most remarkable was the terminal QRS of the BSPM, where the terminal maximum may be right superior anterior, anterior superior, or right posterior, presumably reflecting the right ventricular outflow tract, the superior septum, or the posterior basal left ventricle.
TL;DR: It is concluded that a single bipolar lead from the right subclavian area to lead V5 is adequate in those laboratories that are restricted to testing subjects with a normal electrocardiogram at rest and in patients with a previous infarction or other abnormalities in the Electrocardiograms at rest three (pseudo) orthogonal leads or several standard leads are necessary.
Abstract: To define the optimal lead system for exercise electrocardiography, data of the whole body surface potential distribution were analyzed in 25 normal subjects and in 25 patients with coronary artery disease at rest and during exercise. All patients had a normal electrocardiogram at rest. The sensitivity of the standard chest leads was 60 percent; it improved to 84 percent with the body surface map whereas both methods had a 100 percent specificity. On the basis of these data, and reports from other centers, it is concluded that a single bipolar lead from the right subclavian area to lead V5 is adequate in those laboratories that are restricted to testing subjects with a normal electrocardiogram at rest. In patients with a previous infarction or other abnormalities in the electrocardiogram at rest three (pseudo) orthogonal leads or several standard leads are necessary. Recommendations for optimal measurements from the exercise electrocardiogram are based on quantitative computer analysis of the selected leads in larger groups of patients. Best results were obtained with a combination of S-T amplitude, S-T slope and heart rate. The improvement in sensitivity from 50 percent with visual analysis to 85 percent with computer was similar to that obtained with body surface mapping. Changes of the P wave and QRS complex during exercise appeared to be of little diagnostic value. The pathophysiologic mechanisms that contribute to the changes of the electrocardiogram during exercise are discussed.
TL;DR: Patients with rapid infarction showed high initial ST segment elevation which decreased promptly compared with those with prolonged infarct, who showed moderate but more persistent ST segment Elevation, which was significantly lower thereafter.
Abstract: We have studied the time course of development of ST segment elevation, R wave loss, and Q wave development in 41 patients using 35 lead praecordial mapping or 12 lead electrocardiograms in those with anterior and inferior infarcts, respectively. The first recording was at a mean time of six hours after the onset of pain; subsequent records were taken every eight hours for 24 hours, every 12 hours for the second day, and every day thereafter. Serial CK MB estimates were obtained at every four hours for the first 72 hours. There was good agreement in the time course between the electrocardiogram and enzyme evolution. Forty-one per cent of patients showed rapid infarction with R wave and Q wave evolution complete within 12 hours of pain and accompanied by a short duration of enzyme release (mean = 19.30 hours). Fifty-nine per cent of patients showed more prolonged infarction with longer R wave and Q wave evolution and enzyme release (mean = 30 hours). Four patients also showed delayed reinfarction. ST segment elevation was maximal at six hours in the whole group and was significantly lower thereafter. Patients with rapid infarction showed high initial ST segment elevation which decreased promptly compared with those with prolonged infarction, who showed moderate but more persistent ST segment elevation. This study shows the variability in the time course of the electrocardiogram and enzyme evolution after myocardial infarction in man.
Book•
31 Jul 1981
TL;DR: The value of the electrocardiogram in diagnosing site of origin and mechanism of supraventricular tachycardia with aberrant conduction and its importance in determining diagnosis of pacemaker malfunction is investigated.
Abstract: 1. Prognostic significance of the electrocardiogram in patients with coronary heart disease.- 2. Correlation between electrocardiographic and scintigraphic findings in myocardial infarction.- 3. Assessment of the value of electrocardiographic signs for myocardial infarction in left bundle branch block.- 4. Electrocardiographic diagnostic dilemmas in myocardial ischemia and infarction.- 5. Electrocardiographic diagnosis of myocardial infarction in pacemaker patients.- 6. Relation between exercise electrocardiogram and extent of coronary artery disease.- 7. Prognostic value of limited exercise testing before hospital discharge following myocardial infarction.- 8. Approach to the patient with bundle branch block.- 9. The value of the electrocardiogram in diagnosing site of origin and mechanism of supraventricular tachycardia.- 10. The short PR internal.- 11. The differentiation between ventricular tachycardia and supraventricular tachycardia with aberrant conduction: the value of the 12-lead electrocardiogram.- 12. Relation between site of origin and QRS configuration in ventricular rhythms.- 13. Torsade de Pointes.- 14. Electrocardiographic diagnosis of pacemaker malfunction.- 15. Electrocardiographic changes occurring with advancing age.- 16. The electrocardiogram in digitalis intoxication.- 17. Holter monitoring and cardiac rhythm.- 18. The electrocardiogram in pulmonary embolism.
TL;DR: A microprocessor ECG system was employed capable of averaging multiple QRS complexes to reduce noise and found that myocardial infarction may attenuate high as well as low frequency QRS potentials as part of a general decrease in electromotive force.
TL;DR: LV diastolic filling, evaluated noninvasively by radionuclide angiography, is abnormal in a high percentage of patients with CAD at rest independent of LV systolic function or previous myocardial infarction.
Abstract: Electrophysiologic studies using the His bundle electrogram (HBE) and histologic studies of serial sections of the conduction system were correlated in two groups of deceased patients. Group 1 consisted of five patients with chronic complete atrioventricular block (CAVB) who had narrow QRS complexes and AH block (block proximal to the His bundle deflection). Group 2 consisted of four patients with chronic CAVB who had wide QRS complexes and HV block (block distal to the His bundle deflection). In group 1, the sites of the main lesion were not located in the approaches to the atrioventricular (AV) node or the AV node, but were found in the penetrating portion of the His bundle in one patient and in the branching portion of the His bundle in three patients. In the remaining patient, the main site of block could not be demonstrated histologically in the AV conduction system, but marked fibrosis of the approaches to the sinoatrial node and surrounding atrial muscle was found. In all patients of group 2, the site of the main lesion was located in the bilateral bundle branches, and thus was compatible with so-called trifascicular block. This correlation study between the His bundle electrogram and histologic findings of the AV conduction system showed that in some cases, CAVB presenting as AH block on the HBE can be associated with a lesion in the branching portion of the His bundle (distal His), and that CAVB presenting as HV block on the HBE is associated with a bilateral lesion of the bundle branches.
TL;DR: Three approaches for detecting abnormalities in body surface potential maps recorded from patients with myocardial infarction were evaluated and it is found that the first approach is superior to the other two for detecting surface potential map abnormalities in patients withMyocardial Infarction.
01 Jan 1981
TL;DR: In acute myocardial infarction, experimental and clinical data indicate clearly that hemodynamic effects of NTG are, in adequate conditions, capable of inducing substantial improvement in both regional and global ventricular performance.
Abstract: In acute myocardial infarction, experimental and clinical data indicate clearly that hemodynamic effects of NTG are, in adequate conditions, capable of inducing substantial improvement in both regional and global ventricular performance. Of equal importance would be the effects upon the intensity of the ischemic process. It would add the recruitment of salvagable myocardial jeopardized areas to the indirect effect of reducing pre- and afterload. This second effect, although suggested by reduction of oxygen demands [7], and probably by a more favorable myocardial perfusion through O2-redistribution, still remains controversial. Present difficulties in assessing actual infarct size, lack of precise correlations between electrocardiographic markers of ischemia (i. e., ST and QRS changes) and histological proofs of ischemic injuries, explain this uncertainty.
TL;DR: It is concluded that ischemic-appearing changes of uncertain significance are common in the postdialysis population.
Abstract: We investigated electrocardiographic changes occurring after hemodialysis in 20 male patients with chronic renal failure, changes in the configuration of T wave, ST segment and R wave consistent with ischemia were found in 30, 45 and 75%, respectively. Contrary to prior speculation the R wave height did not vary with the volume changes of body fluid occurring in dialysis. It is concluded that ischemic-appearing changes of uncertain significance are common in the postdialysis population.
TL;DR: Electrocardiograms of patients with severe aortic stenosis who had no evidence of coronary disease were compared with patients with lateral myocardial infarction who hadNo clinical evidence of left ventricular hypertrophy to help resolve the problem.
Abstract: In routine reporting of electrocardiograms, a frequent problem is presented by the presence of repolarisation abnormalities (ST depression and/or T wave inversion) in the lateral leads without the accepted QRS voltage criterion of left ventricular hypertrophy. To help resolve this problem, the electrocardiograms of 41 patients with severe aortic stenosis who had no evidence of coronary disease were compared with the electrocardiograms of 20 patients with lateral myocardial infarction who had no clinical evidence of left ventricular hypertrophy. Nine of the patients with aortic stenosis were found to show repolarisation abnormalities in the lateral leads without the standard voltage criterion of left ventricular hypertrophy. The repolarisation pattern of aortic stenosis could frequently be distinguished from that of coronary disease by the presence of one or more of the following five features: depression of the J point, asymmetry of the T wave with rapid return to the baseline, terminal positivity of the T wave ("over-shoot"), T inversion in V6 greater than 3 mm, and T inversion greater in V6 than in V4.
TL;DR: Although these early electrocardiographic changes probably reflect either marked regional transmural blood flow deprivation or its aftermath, they could not be taken as indices of eventual massive myocardial necrosis since in most of these patients the alterations were followed by development of nontransmuralMyocardial infarction.
Abstract: An unusual electrocardiographic (ECG) pattern was observed in five patients who suffered an acute anterior myocardial infarction. Early in their illness and following resuscitation from ventricular fibrillation (three patients), in the midst of recurrent ventricular irritability prior to development of ventricular fibrillation (one patient), and following a period of seizures (one patient), the ECG showed ST-segment elevation, marked increase in the R-wave amplitude, disappearance of S waves and merging of QRS complexes with the elevated ST segments, ECG patterns noted in these patients were similar to the ones recorded from dogs immediately after ligation of a large coronary artery, and from patients with severe episodes of variant angina. Although these early electrocardiographic changes probably reflect either marked regional transmural blood flow deprivation or its aftermath, they could not be taken as indices of eventual massive myocardial necrosis since in most of these patients the alterations were followed by development of nontransmural myocardial infarction. The possible mechanisms and the implications of such discrepancy between early and late electrocardiographic indicators of injury or necrosis is discussed.
TL;DR: Following the rate of Q wave development in relation to the early ST segment elevation may be of value in assessing GIK effects provided that a qualitative rather than quantitative relationship between the two parameters is accepted.
Abstract: The effect of glucose-insulin-potassium infusion (GIK) on developing myocardial infarction in dogs was evaluated, commencing infusion 30 min after coronary artery ligation (CAL). The parameters studied were: early (60 min after CAL) and late (6½ h after CAL) epicardial ST segment elevation, the change in Q, R, and S waves and certain myocardial metabolic determinations (glycogen, sodium, potassium, dry-wet weight ratio, adenosine triphosphate, creatine phosphate, inorganic phosphate, and lactate). 6½ h after coronary ligation Q wave amplitude was less, the R wave amplitude was greater and the metabolic profile in the infaret zone was less deranged; metabolic improvement was also found in the nonischaemic zone. Sites in which early ST-segment elevation was less with GIK did not predict all the sites in which there was eventual lessened Q wave formation. R wave fall and disturbance of myocardial metabolism. This study supports others showing an effect of GIK in improving the features of developing experimental myocardial infarction. Following the rate of Q wave development in relation to the early ST segment elevation may be of value in assessing GIK effects provided that a qualitative rather than quantitative relationship between the two parameters is accepted.
TL;DR: The approach to the interpretation of electrocardiograms produced by a new unipolar multiprogrammable “committed” DVI pulse generator (Intermedics) during normal function is described.
Abstract: This paper describes our approach to the interpretation of electrocardiograms produced by a new unipolar multiprogrammable “committed” DVI pulse generator (Intermedics) during normal function. The arrhythmias engendered by this new DVI pacemaker may be better understood by conceptualizing the recycling mechanism in terms of a simple atrial pulse generator with two important qualifica-tions: (1) the ventricular stimulus obligatorily follows the atrial stimulus after 155 ms (AV sequential interval); (2) the pulse generator senses ventricular events (via the ventricular electrode) but recycles according to its atrial timing cycle (AA interval). These characteristics lead in turn to two important consequences: at the QA interval (from the onset of a sensed QRS complex to the succeeding atrial stimulus) must be longer than the VA interval (from a ventricular stimulus to the succeeding atrial stimulus) by a period equal to or slightly greater than the AV sequential time. This may be considered to represent a form of bysteresis, by the pacemaker refractory period always starts at the onset of an atrial cycle (AA interval) and therefore occurs after the delivery of an atrial stimulus or after a sensed ventricular event. The above characteristics may cause pacemaker stimuli to fall within the P wave, PR interval, QRS, ST segment and the ascending limb of the T wave during normal function of the pulse generator. Superficially, these peculiarities resemble malfunction and may be quite befuddling but they all occur predictably according to the electronic design of the pulse generator. (PACE, Vol. 4, November-December, 1981)
TL;DR: Changes in the R wave with exercise correlate with the change in the ejection fraction (and hence ventricular function) and with the changes in systolic volume, which may be one of the mechanisms of the response of the R waves.
TL;DR: Though spatial vector length decreased with exercise and correlated with R wave changes, there was a better correlation between changes in the maximal QRS vector angle and R wave amplitude.
TL;DR: The results were correlated with coronary angiographic and echocardiographic findings as mentioned in this paper, showing that exercise-induced changes in the S-T segment and R wave amplitude correlated with the presence or absence of coronary artery disease.
Abstract: Fifty asymptomatic men, 44 (88 percent) of whom were pilots or allied aviation personnel, were referred because of resting ST-T electrocardiographic changes indistinguishable from those of myocardial ischemia Because of the nature of their occupations, cardiac catheterization was performed to establish the presence or absence of coronary artery disease Exercise tests were performed and analyzed retrospectively with respect to exercise-induced changes in the S-T segment and R wave amplitude The results were correlated with coronary angiographic and echocardiographic findings The 50 subjects were classified into two groups: Group I, 5 men with angiographically proved coronary artery disease, and Group II, 45 men without significant coronary arterial obstruction Analysis of the S-T segment changes at peak exercise showed 21 subjects (42 percent) with a positive exercise test and 29 (58 percent) with a negative test All subjects in Group I had a positive test Sixteen subjects (35 percent) in Group II had a false positive result Analysis of exercise-induced changes in R wave amplitude revealed that six subjects had a positive R wave response on the basis of sum of the changes in voltage in the leads measured (Δ∑R) Four of the six subjects had coronary artery disease and the other two were thought to have a cardiomyopathy One subject with coronary artery disease had a negative R wave response Echocardiography revealed five subjects with asymmetric septal hypertrophy; two of these had a positive exercise test and three a negative test on the basis of S-T segment criteria Thus, symptom-limited treadmill exercise testing of asymptomatic men with resting ST-T electrocardiographic changes produced a high incidence rate of false positive results when S-T segment criteria were used, whereas analysis of changes in R wave amplitude yielded only two false positive results, both in men who had evidence of other heart disease
TL;DR: Intermittent PAF was observed in supraventricular premature beats suggesting that PAF might be due to intraventricular conduction disturbances as well as left anterior or posterior hemiblock, and supports the existence of this new type of divisional block of the LBB.
Abstract: There still exist many questions to the human intraventricular conduction system, especially morphology of left ventricular (LV) conduction system. In the present study, LV conduction system was examined by serial histological examinations, and based on these results experimental and clinical subdivision block of the left bundle branch (LBB) were studied electrophysiologically and histopathologically. 1 ) Reconstruction of the human LBB: Human LV conduction system of 14 hearts showed much variability. LV conduction system was a diffuse fan like structure broadly distributed over the left septal surface and always covered diffusely mid-septal area. 2) Experimental subdivision block of the LBB: In the discrete block of the septal Purkinje network (11 dogs), the activation time in the apical area prolonged from 20.0±4.9 msec to 24.5±4.9 msec (p<0.05), and the QRS loop tended to be displaced anteriorly. In the discrete block of the left posterior division (9 dogs), the activation time showed slight prolongation in the posterior basal area, but the QRS waves of the scalar ECG did not change significantly. In the block of the left posterior division and septal Purkinje network ( 11 dogs), epicardial activation delay was observed in a relatively wider area from the apex to the posterior basal area. The maximum QRS vector in the frontal plane shifted rightward (p<0.05). 3) Prominent anterior QRS force (PAF) in clinical electrocardiogram: PAF was observed frequently in patients with ischemic heart disease (12.4%) and diabetes mellitus (8.5%). Serial histological examination of a patient with PAF showed marked fibrosis in the mid-septal fibers in association with fibrosis of the right bundle branch and posterior part of the LBB. Intermittent PAF was observed in supraventricular premature beats suggesting that PAF might be due to intraventricular conduction disturbances as well as left anterior or posterior hemiblock. This intermittency also supports the existence of this new type of divisional block of the LBB. New concepts of intraventricular conduction disturbances must be established including the conduction disturbances of the mid-septal fibers of the LV conduction system.