Showing papers in "Circulation in 1977"

Echocardiographic determination of left ventricular mass in man. Anatomic validation of the method.

Abstract: An accurte echocardiographic (E) method for determination of left ventricular mass (LVM) was derived from systematic analysis of the relationship between the antemortem left ventricular echogram and postmortem anatomic LVM in 34 adults with a wide range of anatomic LVM (101-505 g). No subject had massive myocardial infarction, ventricular aneurysm, severe right ventricular volume overload or hypertrophic cardiography. The best method for LVM-E identified combined cube function geometry with a modified convention for determination of left ventricular internal dimension (LVID), posterior wall thickness (PWT), and interventricular septal thickness (IVST), which excluded the thickness of endocardial echo lines from wall thicknesses and included the thickness of left septal and posterior wall endocardial echo lines in LVID (Penn Convention, P). By this method, anatomic LVM = 1.04 ([LVIDp + PWTp + IVSTp]3--[LVIDp]3) -- 14 g; r = 0.96, SD= 29 g, N= 34. Standard echo measurements gave less accurate results, as did previously reported methods for LVM-E. LVM-Dp is an accurate, widely applicable method for the study of left ventricular hypertrophy.

The wavefront phenomenon of ischemic cell death. 1. Myocardial infarct size vs duration of coronary occlusion in dogs.

Abstract: Irreversible ischemic myocardial cell injury developes in an increasing number of cells as the duration of coronary occlusion is prolonged. The present study quantitates myocardial necrosis produced by 40 minutes, 3 hours, or 6 hours of temporary circumflex coronary occlusion (CO) followed by 2 to 4 days of reperfusion, or by 24 or 96 hours of permanent circumflex ligation in pentobarbital anesthetized open chest dogs. After 40 minutes of ischemia, myocyte necrosis was subendocardial but with increasing duration of coronary occlusion, irreversible injury progressed as a wavefront toward the subepicardium. Transmural necrosis was 38 +/- 4% after 40 min, 57 +/- 7% after 3 hours, 71 +/- 7% after 6 hours and 85 +/- 2% after 24 hours of ischemic injury. These results document the presence of a subepicardial zone of ischemic but viable myocardium which is available for pharmacologic or surgical salvage for at least three and perhaps six hours following circumflex occlusion in the dog.

HDL cholesterol and other lipids in coronary heart disease. The cooperative lipoprotein phenotyping study.

Abstract: The relation between coronary heart disease (CHD) prevalence and fasting lipid levels was assessed by a case-control study in five populations with a total of 6859 men and women of black, Japanese and white ancestry drawn from subjects aged 40 years and older from populations in Albany, Framingham, Evans County, Honolulu and San Francisco. In each major study group mean levels of high density lipoprotein (HDL) cholesterol were lower in persons with CHD than in those without the disease. The average difference was small -- typically 3-4 mg/dl -- but statistically significant. It was found in most age-race-sex specific groups. The inverse HDL cholesterol-CHD association was not appreciably diminished when adjusted for levels of low density lipoprotein (LDL) cholesterol and triglyceride. LDL, totoal cholesterol and triglycerides were directly related to CHD prevalence; surprisingly, these findings were less uniformly present in the various study groups than the inverse HDL cholesterol-CHD association.

Quantitative coronary arteriography: estimation of dimensions, hemodynamic resistance, and atheroma mass of coronary artery lesions using the arteriogram and digital computation.

Abstract: More accurate characterization of coronary artery lesions is needed for evaluation of short and long-term interventions in coronary disease. A method of segmental artery analysis has been developed to maximize the information obtained from coronary arteriograms. Coronary lesions are traced from two projected, perpendicular, 35 mm cineangiographic views and transmetted, in digital form, to a PDP 11/45 computer. Magnification and distortion of the image are compensated for in order to determine the actual vessel profiles, using the catheter and its location as a scaling device. The two views are matched; a spatial representation of the vessel centerline is constructed mathematically; and orthogonal vessel diameters are computed at increments along this centerline. Assuming an elliptical lumen, the absolute and percentage reduction in diameter and cross-sectional area in the stenosis are computed. More complex functions (integrated atheroma mass, Poiseuille resistance, and orifice resistance) are then calculated. The accuracy and variability of the different steps involved in lesion analysis have been determined. Dimensional accuracies of +/- 150 microns (SD) are feasible. Examples are given of patients with Prinzmetal's angina and with progressive coronary disease.

A critical review of the systolic time intervals.

Abstract: The theoretical basis for the use of the systolic time intervals has been largely established The method has been validated by direct measures from within the circulatory system Standards for equipment and technique have been defined Numerous clinical studies have demonstrated the value of this quantitative noninvasive technique for assessing left ventricular performance At present there is need for further studies of the clinical usefulness of the systolic time intervals to improve both diagnosis and therapy of various cardiovascular disorders

Contractile state of the left ventricle in man as evaluated from end-systolic pressure-volume relations.

Abstract: End-systolic pressure (PES), volume (VES), wall tension (TES) and circumference (CES) of the human left ventricle were studied at cardiac catheterization in 24 subjects with varying degrees of left ventricular dysfunction. Acute alterations in systolic load consistently resulted in changes in VES and CES, with a smaller volume and circumference characterizing the lower systolic load in each subject. End systolic pressure-volume lines were constructed by plotting PES against VES at the higher and lower systolic load in each subject. The slope of the resultant lines was considerably steeper for normal than for poorly contractile left ventricles. Vo, the volume axis intercept of the line (i.e., the theoretical VES at PES = O) was significantly smaller for normal than for poorly contractile ventricles. Similar findings were noted for Co, the theoretic end-systolic circumference at zero end-systolic ventricular wall tension. Post-extrasystolic potentiation resulted in decreased VES and CES with no change in PES and only a slight fall in TES. In conclusion, end-systolic pressure-volume and tension-circumference relations reflect the contractile state of left ventricular myocardium. Quantitation of these relationships may provide a useful new approach to the assessment of myocardial function in man.

Differentiation of transiently ischemic from infarcted myocardium by serial imaging after a single dose of thallium-201.

Abstract: Myocardial 201Tl uptake and regional blood flow by the microsphere technique were determined in anesthetized dogs undergoing either 20 min of coronary occlusion and 100 min of reperfusion (N = 10) or 120 min of occlusion (N = 4). In both groups, 201Tl was injected intravenously after 10 min of occlusion. In transiently occluded dogs, regional flow at the time of 201Tl administration was reduced to 8 +/- 3% of normal flow in endocardial layers of the central ischemic zone. After 100 min of reperfusion, flow values were not significantly different from normal. 201Tl activity after reperfusion rose to 56 +/- 5% of normal, demonstrating that redistribution of the radionuclide occurred during the reflow period. In animals with persistent occlusion, there was a significant relationship between 201Tl uptake and flow (r = 0.95) and no evidence of redistribution of 201Tl during the two hour occlusion period. In another five dogs receiving 201Tl, serial gamma camera images obtained during reperfusion showed increasing uptake of the tracer in apical defects which returned to normal by 4 hours of reflow. Thirteen patients with stable angina received 2 mCi of 201Tl intravenously at peak exercise, and multiple gamma camera images obtained serially. All demonstrated zones of diminished 201Tl uptake 10 min after exercise. Defects which partially or completely disappeared within 1-6 hours postexercise corresponded to areas supplied by coronary arteries with significant stenoses. Persistent defects were present in regions of old myocardial infarction. Six additional patients with acute myocardial infarction demonstrated 201Tl myocardial defects which showed no significant change over 6 hours. Thus, redistribution of 201Tl into ischemic myocardium was demonstrated during transient coronary occlusion in dogs and after exercise stress in man. Sequential imaging after a single dose of 201Tl at the time of exercise may provide a means for distinguishing between transient perfusion abnormalities or ischemia and myocardial infarction of scar.

Echocardiographic assessment of a normal adult aging population.

Abstract: Echocardiograms were performed on 105 male participants in the National Institutes on Aging's volunteer Longitudinal Study Program. All subjects (25--84 years of age) were physically active and had no evidence of hypertension or cardiovascular disease. Measurements were made of the initial diastolic (E-F) slope of the anterior mitral valve leaflet, the aortic and left ventricular cavity dimensions, and the thickness of the posterior left ventricular wall. Fractional shortening of the minor semi-axis of the left ventricle and the velocity of circumferential fiber shortening were also determined. It was found that increasing age correlated with a decrease mitral valve E-F slope and increased aortic root diameter and left ventricular wall thickness. Aging did not affect left ventricular cavity dimension, fractional shortening of the minor semi-axis, and velocity of circumferential fiber shortening. These findings suggest that aging in the normal male is associated with altered left ventricular diastolic filling, increased aortic root diameter and left ventricle hypertrophy but little change in contractile ability in the resting state.

Arteriographic evidence of coronary arterial spasm in acute myocardial infarction.

Abstract: Coronary arteriography was performed before and after the intracoronary injection of nitroglycerin to determine the presence or absence of spasm in patients within the first 12 hours of acute myocardial infarction. Coronary arterial spasm was demonstrated in six of fifteen (40%) acute myocardial infarctions associated with coronary artery disease. In five of the six instances the interval from the onset of symptoms to arteriography was less than 6 hours. Spasm was superimposed on a high-grade atherosclerotic obstruction and was separated from the catheter tip by a segment of normal vessel in each instance. The coronary artery remained patent (following the initial relief of spasm) in two patients maintained on sublingual nitrates and heparin. Spasm, superimposed on an atherosclerotic obstruction, may be the primary event or a secondary occurrence in the pathophysiology of acute myocardial infarction. Catecholamines could play an important role in the early pathophysiology of acute myocardial infarction by producing spasm and/or platelet aggregation at the site of an atherosclerotic obstruction. A dynamic interaction between spasm, platelet aggregates and the atherosclerotic plaque may precede coronary thrombosis.

Re-entrant ventricular arrhythmias in the late myocardial infarction period. 1. Conduction characteristics in the infarction zone.

Abstract: Dogs 3-7 days following ligation of the anterior descending coronary artery representing a remarkably stable model for re-entrant ventricular arrhythmias (RVA) and allowed detailed electrophysiologic studies of the re-entrant mechanism. In these dogs, we could regularly illustrate the presence of continuous electrical activity originating from the infarction zone (IZ) and bridging the diastolic interval between the initiating and re-entrant beats as well as between consecutive re-entrant beats. Conduction in the IZ was highly complex, with multiple potentially re-entrant pathways, functionally dissociated areas, and areas of localized ventricular fibrillation. Conduction disorders in ischemic myocardium were consistently tachycardia-dependent with the spontaneous onset of RVA specifically associated with a Wenckebach-like conduction pattern in a potentially re-entrant pathway. Both manifest and concealed re-entry, as well as re-entrant beats with regular extrasystolic grouping, constant or variable coupling, uniform multiform and bidirectional QRS configurations, were related to characteristic conduction patterns in the IZ. In summary, the study provides the first direct in vivo evidence of ventricular re-entry and demonstrates propensity for RVA and sudden death in the late myocardial infarction period.

Autopsy study of unoperated abdominal aortic aneurysms. The case for early resection.

Abstract: A review of 24,000 consecutive autopsies during a 23-year period from 1952 through 1975 at the Massachusetts General Hospital revealed 473 patients died with surgically intact arteriosclerotic abdominal aortic aneurysms (AAA) Contrary to previous studies, the incidence of rupture of AAA between 4 and 7 cm in our experience is similar and significant (25%) The location of rupture and duration of symptoms were recorded Of the multiple-risk factors considered, only size seemed to bear on the likelihood of AAA rupture Of 52 patients followed 3 months to 10 years before death with known AAA, the majority died of the ruptured AAA In a surgical environment with an expected mortality of less than 2%, even small aortic aneurysms should be resected

Variability in the analysis of coronary arteriograms.

Abstract: Variability in coronary arteriogram readings was studied by having cine films from ten patients read by eleven readers Three of the eleven subsequently met as an expert panel to provide a joint evaluation which could serve as a standard Considerable variability was found between individual readers and between readers and the panel The average standard deviation for estimation of any segmental stenosis by any single reader was 18% Disagreement about the number of major vessels with a 70% stenosis occurred 31% of the time Discrepancies were most likely to occur in analyzing distal arterial segments, in reading nonopacified segments, and during analysis of films showing more severe disease or having poorer technical quality Recent experience in reading arteriograms seemed to be the most important characteristic in determining the accuracy of a reader A protocol for the use of three readers is suggested

The effect of acute coronary artery occlusion on subepicardial transmembrane potentials in the intact porcine heart.

Abstract: Subepicardial transmembrane potentials were recorded from intact pig hearts to observe the changes induced by acute ischemia. Ischemia shortened action potential duration, and decreased its amplitude, upstroke velocity, and resting potential. The cells were unresponsive after 12 to 15 minutes of coronary artery occlusion, yet near normal action potentials could be restored by flushing the occluded artery with saline as late as 40 minutes after occlusion. The unipolar extracellular electrogram reflected unresponsiveness by a monophasic potential. Local refractory periods initially shortened by up to 100 msec. Later, postrepolarization refractoriness occurred and refractory periods lengthened often in excess of basic cycle length, thus resulting in 2:1 responses. The onset of early ventricular arrhythmias often coincided with a period of alternation and 2:1 responses, especially when these got out of phase in different regions. Reperfusion frequently led to ventricular fibrillation, and was associated with marked inhomogeneity in cellular responses. Re-entry within ischemic myocardium was the most likely mechanism for arrhythmias.

Thallium-201 myocardial perfusion imaging at rest and during exercise. Comparative sensitivity to electrocardiography in coronary artery disease.

Abstract: The sensitivity of myocardial perfusion imaging (MPI) using thallium-201 injected both at rest and during peak exercise was compared to simultaneously recorded 12 lead electrocardiography (ECG) for the detection of transient ischemia in 20 normal subjects and 63 patients with coronary artery disease (CAD). No significant perfusion defects or ECG changes were seen on either the rest or exercise studies in any of the normal subjects. Fifty-six percent of patients with CAD developed new perfusion defects with exercise compared to 38% who developed ischemic ST-segment depression (P less than 0.02). However, when chest pain and/or ST depression were considered indices of ischemia, the sensitivity of exercise testing and thallium-201 MPI was similar. The increased sensitivity of MPI compared to ST-segment depression on the ECG was due to patients with baseline ECG abnormalities and those who failed to achieve 85% of predicted maximum heart rate with exercise. Analysis of the exercise results according to the extent of coronary artery disease revealed a progressive increase in both positive ECGs and MPI with the number of vessels involved. In patients with single vessel disease the MPI was more sensitive than the ECG (P less than 0.02). The combination of the rest and exercise ECG, MPI and chest pain during exercise failed to identify 11% of patients with CAD. Exercise thallium-201 MPI is a useful adjunct to conventional exercise testing particularly when evaluating patients with abnormal resting ECGs, those who develop ventricular conduction defects of arrhythmias during exercise, and those who fail to achieve their predicted heart rate because of fatigue or breathlessness.

Myocardial imaging with thallium-201 at rest and during exercise. Comparison with coronary arteriography and resting and stress electrocardiography.

Abstract: Myocardial imaging with intravenous thallium-201 (201Tl) was performed at rest and following maximal treadmill exercise in 101 patients with suspected coronary artery disease. Results were interpreted from Polaroid scintiphotos by three independent observers with complete interobserver agreement in 79%. Of 25 patients with no or insignificant coronary artery disease (less than 50% diameter stenosis), one (4%) had a resting 201Tl image defect, one (4%) had an exercise 201Tl defect, none had an ECG Q wave, and four (16%) had exercise ST-segment depression. Among 76 patients with coronary artery disease (greater than or equal to 50% diameter stenosis), 58 (76%) had a defect on either the rest or exercise 201Tl image. The proportion of patients with an exercise image defect (50/76, 66%) was greater than the proportion with exercise ST depression alone (34/76, 45%; P less than 0.02). Overall, 69 of the 76 (91%) patients with coronary artery disease had either a positive rest or exercise myocardial image and/or a positive rest (ECG Q waves) or exercise (ST depression) electrocardiogram. This exceeded the proportion with only rest or exercise electrocardiographic abnormalities (50/76, 65%; P less than 0.001). We conclude that rest and exercise myocardial imaging with 201Tl is easily accomplished with readily available imaging equipment. The image data enhanced the diagnostic sensitivity of stress electrocardiography, and provided spatial identification of the abnormal segment(s) of myocardium.

Entrainment and interruption of atrial flutter with atrial pacing: studies in man following open heart surgery.

Abstract: To examine the question of why the pacing rate and duration of atrial pacing are crucial factors in the successful interruption of atrial flutter, studies were performed on 30 patients in the period following open heart surgery. In each patient the diagnosis of atrial flutter was made using a pair of wire electrodes placed on the right atrial epicardium at the time of operation and brought out through the anterior chest wall. The same electrodes were used for atrial pacing. Pacing faster than the spontaneous rate of the atrial flutter which failed to interrupt the atrial flutter was associated with transient entrainment of the atrial flutter up to the atrial pacing rate. Atrial flutter was interrupted successfully when the atria were paced at a rate which was too fast for the atrial flutter to follow. This was heralded by the conversion of previously negative flutter waves to positive atrial complexes in ECG lead II. When pacing the atria at a constant rate, 2-22 seconds with a mean of 10 seconds were required to interrupt the atrial flutter.

Alcohol consumption, cardiovascular risk factors, and mortality in two Chicago epidemiologic studies.

Abstract: Multivariate analysis of the association at baseline between problem drinking and cardiovascular risk factors among 1,233 white male employees of the Chicago Peoples Gas Company age 40-59 showed the 38 problem drinkers with significantly higher blood pressures and cigarette consumption and significantly lower relative weights than the others. Similar analysis among 1,899 white male employees of the Hawthorne Works of the Western Electric Company in Chicago age 40-55 showed the 117 men consuming 5 or more drinks per day with significantly higher blood pressures and cigarette use than the others. No significant differences were recorded between heavy drinkers and the others in serum cholesterol level. The gas company problem drinkers had significantly higher 15-year mortality rates from all causes, cardiovascular diseases, coronary heart disease, and sudden death. These differences could not be entirely explained by their blood pressure, smoking, and relative weight status. The Western Electric heavy drinkers had increased 10-year mortality rates both for all causes and noncardiovascular causes.

Analysis of left ventricular function from multiple gated acquisition cardiac blood pool imaging. Comparison to contrast angiography.

Abstract: Global ventricular function was evaluated by both multiple gated cardiac blood pool scans (MUGA) and contrast ventriculograms in a group of 17 patients with suspected coronary artery disease. The contrast ventriculograms were analyzed frame by frame to generate a volume versus time curve for each patient, while the tracer data were analyzed by two methods: 1) the standard method, in which the left ventricle is identified on the end-diastolic frame and the background corrected activity under the region of interest obtained from the entire cardiac cycle, and displayed as a time versus activity curve; and 2) by a semi-automatic method in which the computer applies a threshold detection program to define the ventricular borders, and activity in the chamber at each point in the cardiac cycle is defined after background correction. The tracer data in each patient were analyzed independently by four observers. The tracer data correlated with the contrast data on a point by point basis r = 0.87 for the standard method, and 0.93 for the semi-automatic technique. An F test of variance revealed the semi-automatic method superior to the standard approach (P less than 0.05).

Congenital heart block in newborns of mothers with connective tissue disease.

Abstract: Of 22 children with congenital complete heart block (CCHB) available for study, 14 (63.6%) were born to 11 mothers with clinical or laboratory evidence of connective tissue disease, primarily lupus erythematosus (LE). Seven mothers had both clinical and laboratory evidence of disease while four had only positive laboratory studies including fluorescent antinuclear antibody, rheumatoid factor, and depressed complement levels. In adults with systemic LE, pathologic changes in the collagen surrounding the conduction system have led to the fibrosis and death from heart block. Antinuclear antibodies of the IgG class cross the placental barrier and newborn infants have been reported with transient skin lesions of lupus. Placental transmission of such antibodies may affect the fetal cardiac conduction system, surrounding collagen, and myocardium, leading in some cases to CCHB. This is probably one important etiologic factor in CCHB even though the mother is asymptomatic during her pregnancy.

Prediction of the normal blood volume. Relation of blood volume to body habitus.

Abstract: Predictions of blood volume (BV) assume the existence of a constant ratio between BV and body weight or surface area (SA). We examined the validity of this assumption by calculating BV from plasma volume and body hematocrit in 160 normal volunteers whose weights ranged from -38.7 to 210.8% of desirable weight (assessed by a modification of the Metropolitan Life Insurance Company Desirable Weight tables). BV is not a constant fraction of body weight or SA in this population. Its prediction from such constant ratios results in a large error of estimate which is systematically biased with respect to height and weight. BV prediction from the observed regressions of the parameter on weight and SA reduces the error substantially but remains biased with respect to height. BV prediction from the subject's degree of deviation from desirable weight affords a smaller error of estimate which is apparently free from systematic bias.

Re-entrant ventricular arrhythmias in the late myocardial infarction period. 2. Patterns of initiation and termination of re-entry.

Abstract: The electrophysiologic mechanisms for the initiation and termination of re-entrant ventricular arrhythmias (RVA) were critically analyzed in dogs 3-7 days following ligation of the anterior descending coronary artery, utilizing direct recordings of the re-entrant pathway (RP) from the epicardial surface of the infarction zone. Re-entry could occur during a regular cardiac rhythm if the heart rate is within the narrow critical range during which conduction in a potentially RP exhibits a Wenckebach-like (W) pattern with a beat-to-beat increment of conduction delay until the activation waveform is sufficiently delayed to re-excite normal myocardium. If a regular cardiac rhythm is associated with limited conduction delay in a potentially RP, premature beats within a critical range of coupling intervals could result in sufficient conduction delay to induce re-entry. Re-entrant ventricular arrhythmias may be unmasked on abrupt termination of a critical fast rate of cardiac pacing only if pacing was terminated during those beats of a W pattern associated with marked conduction delay in a RP. RVA could be ended by one or more properly timed premature beats that would pre-excite part of the RP. An electrophysiologic mechanism for R-on-T and its relationship to onset of ventricular fibrillation was shown, based on markedly delayed RP conduction of the beat prior to the one apparently coupled to the premature beat.

Longitudinal dissociation in the His bundle. Bundle branch block due to asynchronous conduction within the His bundle in man.

Abstract: This report presents electrophysiological data in 27 patients (out of a series of 110) which suggest longitudinal dissociation in the His Bundle (BH). Twenty-five patients showed left bundle branch block (LBBB) which was rate related in three and two had isolated left axis deviation (LAD) with narrow QRS complexes. BH recordings were performed via the right heart, and in each patient the same electrode catheter was used for stimulation of the BH at different sites. The H-V time was prolonged (range 50-70 msec, mean 59) in all 22 patients with constant LBBB, in one of the three of the rate related LBBB, and in one of the two with isolated LAD; and remained unchanged throughout. In all 25 patients with LBBB proximal BH stimulation exhibited QRST complexes identical to those with normal sinus rhythm with a PI-R interval equal to the H-V time. BH stimulation at a constant cycle length, but at a slightly distal site, abolished the LBBB (constant or rate related) and resulted in narrow QRS complexes (_ 95 msec) with a PI-R interval shorter than the H-V time by 5 to 20 msec. In the two patients with isolated LAD, BH stimulation abolished LAD with a PI-R interval identical to the H-V time. These findings suggest that a bundle branch block pattern and/or axis deviation may result from a focal lesion or an area of altered refractoriness within the BH. The duration of the QRS complexes and/or a shift in QRS axis was normalized by BH stimulation distal to the lesion due to synchronous impulse conduction to both the bundle branches.

The extraction of thallium-201 by the myocardium.

Abstract: The concentration of thallium-201 in the myocardium immediately following injection of tracer is the result of both blood flow delivering tracer to the heart and extraction by the myocardium. In these studies, the extraction of thallium-201 by the canine myocardium was determined as a function of heart rate, coronary blood flow, hypoxia, changes in pH, and following administration of propranolol, insulin, and strophanthin. Under basal conditions, extraction fraction measured 88 +/- 2.1%, following pacing to a rate of 195 beats/min extraction fraction remained unchanged at 88.5%. Similar results were found with changes in pH, propranolol, insulin, and strophanthin. Hypoxia caused a significant decrease in extraction fraction to 77.9%. When coronary blood flow was increased in excess of demands by drugs, extraction fraction fell logarithmically.

Correlation of postmortem anatomic findings with electrocardiographic changes in patients with myocardial infarction: retrospective study of patients with typical anterior and posterior infarcts

Abstract: This retrospective study correlates electrocardiographic and histopathologic findings in 24 patients with single well-circumscribed infarcts to determine 1) whether ECG terms commonly used to describe the location of myocardial infarcts are significant, and 2) whether the extent of infarct can be determined using QRS characteristics. Transverse sections of the hearts were photographed. Based on histologic sections, the infarct was outlined on the photograph and each section was planimetered via a sonic digitizer into a computer that was programmed to divide the left ventricle into 8 radial sectors and also into basal, mesial, and apical thirds. The percentage of infarct in each of these areas was then calculated. Of the 24 hearts evaluated 12 had posterior infarcts and 12 had anterior infarcts. Posterior infarcts principally involved the basal and mesial levels, whereas the anterior infarcts were more extensive in the apical and mesial thirds, with relative or total sparing of the base. Posterior infarcts were associated with Q waves in leads II, III and aVF in 11 instances. The other posterior infarct was associated with markedly diminished R waves in leads II, III and aVf in the presence of a horizontal axis. All anterior infarcts were associated with Q waves or markedly diminished R waves in the right precordial leads. Eight of the anterior infarcts exhibited circumferential apical involvement and all eight were associated with Q waves or markedly diminished R waves in the left precordial leads. This study documents the electrocardiographic identification of anterior, posterior, and apical infarcts by correlation with pathologic anatomy.

Evaluation of left ventricular size and function by echocardiography. Results in normal children.

Abstract: Left ventricular (LV) size and function were studied by echocardiography in 145 normal children. The LV end-diastolic diameter (EDD) and its percentage change with systole (%deltaLVD) were measured and mean velocity of circumferential fiber shortening (Vcf) calculated. The LV pre-ejection period (PEP) and ejection time (LVET) were determined from recordings of aortic valve motion. The EDD increased by approximately threefold during childhood and was best correlated with the log of body weight (r = 0.95) and the log of body surface area (r = 0.96). The mean %deltaLVD was 36 +/- 4 (SD), and this index of LV function was independent of age and heart rate. Mean Vef was higher, and the absolute values of PEP and LVET shorter, in younger children with a faster heart rate. The mean ratio of PEP/LVET was 0.31 +/- 0.003, and was relatively independent of age (r = 0.41) and heart rate (r = 0.37). The %deltaLVD and PEP/LVET appear to be particularly useful indices of LV function because they remain constant during the course of childhood.

Exercise stress testing.

Abstract: ALTHOUGH EXERCISE STRESS TESTING FOR CARDIAC PATIENTS has been in use for nearly 50 years, widespread acceptance of the technique as an important diagnostic tool in cardiology has been accomplished only recently. This has occurred with the recognition that patients with cardiac disease, even in advanced degree, can perform exercise safely under controlled conditions, and that objective information regarding cardiac functional capacity and the presence or absence of myocardial ischemia can be determined. In addition, epidemiologic follow-up studies and correlative studies comparing exercise electrocardiographic findings with coronary arteriograms have provided documentation of the sensitivity and specificity of the test in patients with coronary artery disease. In spite of considerable scientific input into this field in the last ten years, controversy regarding the usefulness and role of exercise stress testing in a variety of clinical settings persists.' This review will consider those aspects of exercise testing most relevant to the practicing physician. Several comprehensive monographs dealing with various aspects of this field have been published recently.2-8 The reader is referred to these sources for technical details or further discussion of some of the material covered here.

Accelerated "atherosclerosis". A morphologic study of 97 saphenous vein coronary artery bypass grafts.

Abstract: Intimal thickening of uncertain cause has been noted in saphenous vein bypass grafts. To study the development of these changes, 97 vein grafts in 55 autopsied patients were examined by angiography and histology. Significant alterations in the grafts were confined to the intima and included thin layers of circumferential thrombus, concentric fibrous plaque and occlusive thrombus with organization. Circumferential nonocclusive intimal thrombus was present in 36 (73%) postoperative patent grafts. Concentric fibrous plaque, found in all twelve patent late grafts, showed changes characteristic of atheromata, including smooth muscle and foam cells. Intimal fibroelastosis was absent in the grafts, indicating that concentric plaque is not a simple response to increased pressure, or an "arterialization" of the vein. The findings suggest that early appearing concentric intimal thrombus is converted into fibrous plaque, and that this early thrombus is a factor in the development of acclereated "atherosclerosis" in saphenous vein bypass grafts.

Myocardial consequences of coronary artery bypass graft surgery. The paradox of necrosis in areas of revascularization.

Abstract: Myocardial infarction after coronary artery bypass graft (CABG) surgery has been described clinically in up to 30% of patients but there is little morphologic information about the character and pathogenesis of the myocardial injury. We studied myocardium in the distribution of bypassed and nonbypassed coronary arteries for the presence of contraction band necrosis as compared to coagulation necrosis, in 58 autopsied patients who died less than 1 month after surgery. Operation related necrosis consisting of focal subendocardial contraction band necrosis was present to some degree in 48 (83%) patients. Regional transmural necrosis was present in 22 (38%) patients and was of two types. Contraction band necrosis occurred in 18 patients and was in the distribution of a patent bypassed coronary artery in 15 of them. Coagulation necrosis was found in four patients, and in each was in the distribution of a new graft-releated coronary artery occlusion. The results suggest that coronary artery reflow through widely patent grafts following the period of operative nonperfusion, rather than graft or intrinsic coronary artery occlusion, accounts for the majority of operation-related myocardial "infarcts" associated with CABG surgery. Thus, prevention of intraoperative myocardial injury must also focus on characteristics of the phase of myocardial reperfusion.

Assessment of cardiac performance with quantitative radionuclide angiocardiography: sequential left ventricular ejection fraction, normalized left ventricular ejection rate, and regional wall motion.

Abstract: Sequential quantitative first pass radionuclide angiocardiograms (RA) were used to measure left ventricular ejection fraction (LVEF) and left ventricular ejection rate (LVER), and to assess regional wall motion (RWM) in the anterior (ANT) and left anterior oblique (LAO) positions. Studies were obtained with a computerized multicrystal scintillation camera suitable for acquiring high count-rate data. Background was determined in a new fashion by selecting frames temporally from the left ventricular region of interest time-activity curve. A ''representative'' cardiac cycle was formed by summing together counts over three to six cardiac cycles. From this background corrected, high count-rate ''representative''cardiac cycle, LVEF, LVER, and RWM were determined. In 22 patients with normal sinus rhythm in the absence of significant valvular regurgitation, RA LVEF correlated well with that measured by contrast angiography (r = 0.95). LVER correlated well with LVEF measured at contrast angiography (r = 0.90) and allowed complete separation of those with normal (LVER = 3.4 +- 0.17 sec/sup -1/) and abnormal (LVER = 1.22 +- 0.11 sec/sup -1/) (P < 0.001) left ventricular performance. This separation was independent of background. Isoproterenol infusion in five normal subjects caused LVER to increase by 81 +- 17% while LVEF increased by 10 +- 2.0%.more » RWM was correctly defined in 21/22 patients and 89% of left ventricular segments with abnormal wall motion.« less