Showing papers on "QRS complex published in 1990"

An approach to cardiac arrhythmia analysis using hidden Markov models

Abstract: A new approach to ECG arrhythmia analysis is described. It is based on hidden Markov modeling (HMM), a technique successfully used since the mid 1970s to model speech waveforms for automatic speech recognition. Many ventricular arrhythmias can be classified by detecting and analyzing QRS complexes and determining R-R intervals. Classification of supraventricular arrhythmias, however, often requires detection of the P wave in addition to the QRS complex. The HMM approach combines structural and statistical knowledge of the ECG signal in a single parametric model. Model parameters are estimated from training data using an iterative, maximum-likelihood reestimation algorithm. Initial results suggest that this approach can provide improved supraventricular arrhythmia analysis through accurate representation of the entire beat, including the P-wave. >

Significance of initial ST segment elevation and depression for the management of thrombolytic therapy in acute myocardial infarction. European Cooperative Study Group for Recombinant Tissue-Type Plasminogen Activator.

Abstract: To determine the ability of initial ST segment elevation and depression to predict infarct size limitation by thrombolytic therapy, data were analyzed in 721 patients with acute myocardial infarction who were admitted to a randomized, placebo-controlled study of intravenous recombinant tissue-type plasminogen activator. Patients with QRS duration of 120 msec or more or with previous history of myocardial infarction were excluded, leaving 322 in the treatment and 333 in the placebo group. Cumulative 72-hour release of alpha-hydroxybutyrate dehydrogenase and global ejection fraction as well as left ventricular wall motion derived from angiography were used as independent measures of infarct size. Electrocardiograms obtained at admission, 6 hours after start of therapy, and before discharge were analyzed. All ST measurements were made by hand at the J point and 60 msec after the J point. Patients with high ST segment elevation at admission (i.e., sum of ST elevation at 60 msec after the J point was 20 mm or more) had significantly larger infarction and higher hospital mortality when compared with those with lower (less than 20 mm) ST elevation. Reciprocal ST segment depression also showed a linear relation with infarct size and mortality, independent from ST elevation, both in anterior and inferior myocardial infarction. The sum of deviations measured at the J point and 60 msec after the J point differed significantly, especially in anterior myocardial infarction at admission (mean, 16 +/- 9 versus 23 +/- 11 mm). The prognostic value of one measurement was not, however, superior over the other. Treatment with recombinant tissue-type plasminogen activator was most effective in those with large ST deviations at admission, but patients with anterior infarction and smaller ST shifts also appeared to benefit from therapy. Results in individual patients were variable, and the overall correlation of initial ST shifts with enzymatic infarct size was rather low. In conclusion, the present study shows that the magnitude of initial ST elevation and also of reciprocal ST depression in the admission electrocardiogram is valuable for the management and assessment of thrombolytic therapy in patients with acute myocardial infarction.

Pacing systems and methods for control of the ventricular activation sequence

Abstract: Apparatus and methods for improving the ventricular activation sequence of the heart by pacing at an advantageous selected ventricular location to achieve shortening of the QRS complex or pacing at multiple advantageous selected ventricular locations, either simulataneously or with a programmed delay or delays between firings, to achieve shortening of the QRS complex in combination with producing a desirable and efficient ventricular motion. During a cardiac cycle initiated by intrinsic cardiac activity, stimulating impulses may be directed to advantageous selected locations of the ventricles by employing intrinsic cardiac signals to trigger the stimulating impulses, either simultaneously or with a programmed delay or delays between the sensed event or events and firing event or events, to provide improved mechanical and electrical ventricular function.

Functional role of the epicardium in postinfarction ventricular tachycardia. Observations derived from computerized epicardial activation mapping, entrainment, and epicardial laser photoablation.

Abstract: BACKGROUND Conventionally, monomorphic sustained ventricular tachycardia in patients with remote myocardial infarction is believed to originate from the subendocardium. In a previous study, we demonstrated that electrical activation patterns during ventricular tachycardia occasionally suggest a subepicardial rather than subendocardial reentry. METHODS AND RESULTS This study prospectively evaluated the functional role of the epicardium in postinfarction ventricular tachycardia with complex intraoperative techniques including computerized electrical activation mapping, entrainment, observation of changes in activation pattern during successful epicardial laser photoblation, and histological study. Five of 10 consecutive patients undergoing intraoperative computerized activation mapping had 10 ventricular tachycardia morphologies displaying epicardial diastolic activation These 10 "epicardial" ventricular tachycardias revealed the following global activation patterns: monoregional spread (two), figure-eight activation (five), and circular macroreentry (three). Entrainment of ventricular tachycardia using epicardial stimulation was successfully performed from an area of slow diastolic conduction in four tachycardia morphologies. During entrainment, global activation remained undisturbed with recordings showing a long stimulus to QRS interval, unchanged QRS morphology, and pacing capture of all components of the reentry circuit. Neodymium:yttrium aluminum garnet laser photocoagulation was delivered during ventricular tachycardia to epicardial sites of presumed reentry. Epicardial photoablation terminated five of five figure-eight tachycardias, two of three circular macroreentry tachycardias but not the monoregional tachycardias. Electrophysiological recordings during epicardial laser photocoagulation demonstrated progressive prolongation of ventricular tachycardia cycle length and apparent interruption of the presumed reentrant circuit. Histological evaluation of the reentrant region (three patients) showed a rim of surviving myocardium under the epicardial surface. CONCLUSIONS This study suggests that 1) chronic postinfarction ventricular tachycardia may result from subepicardial macroreentry, 2) slow conduction within the reentry circuit can be localized by computerized mapping and epicardial entrainment, and 3) ventricular tachycardia interruption by laser photocoagulation results from conduction delay and block within critical elements of the reentrant pathway. Viable subepicardial muscle fibers may constitute the underlying pathology.

Surface ecg frequency analysis system and method based upon spectral turbulence estimation

Abstract: Frequency domain ECG signal processing systems and methods plot spectral maps and compute statistical parameters from surface electrocardiographic signals, which plots and parameters reveal abnormalities of electrical conduction within the hearts of patients at risk of ventricular tachycardia. Fourier analysis of short overlapping time segments of QRS ECG signal are used to create three dimensional spectral maps disclosing changes in the frequency spectral content of the ECG signal over the whole QRS region. Correlations and statistical evaluations of the spectral content between QRS time segment pairs quantify the spectral turbulence of the ECG and distinguish those at risk from ventricular tachyarrhythmias.

Cardiac involvement in bone marrow transplantation: electrocardiographic changes, arrhythmias, heart failure and autopsy findings.

Abstract: In order to evaluate cardiac involvement in bone marrow transplantation (BMT) we reviewed serial electrocardiograms, chest X-rays and cardiac pathology at autopsy in 45 consecutive adult patients undergoing BMT for hematologic malignancies at our institution. All patients were pretreated with cyclophosphamide (CY, 120 mg/kg) and total body irradiation (TBI, 10-12 Gy). A total of 15 patients developed electrocardiographic ST-segment or T-wave changes and/or arrhythmias post-BMT; four of them also suffered from congestive heart failure. The arrhythmias included frequent ventricular extrasystoles (two patients), paroxysmal atrial fibrillation (one patient), repeated supraventricular tachycardia (one patient) and QT-prolongation with ventricular tachyarrhythmias (one patient). Twelve patients showed an early drop of the total QRS voltage sum exceeding 15% of the pretransplant reading. In a subgroup of five patients the voltage drop was associated with ST-segment or T-wave changes; three of them developed congestive heart failure. At autopsy in 15 patients, the heart weight was on the average 113% of predicted. Myocardial edema, fibrosis and cellular hypertrophy were the most common microscopic findings. Two patients had marantic endocarditis of the aortic valve. Thus, in our experience clinically significant heart involvement affects 5-10% of patients undergoing BMT after pretreatment with CY and TBI. While cardiac complications are generally not a major problem of BMT, they may have serious consequences for individual patients and should therefore be carefully watched for in the treatment of BMT recipients.

Body surface mapping of ectopic left and right ventricular activation. QRS spectrum in patients without structural heart disease.

Abstract: The value of simultaneous 62-lead electrocardiographic recordings in localizing the site of origin of ectopic ventricular activation in a structurally normal heart was assessed by examining body surface QRS integral maps in 12 patients during left and right ventricular (LV and RV) pacing at 182 distinct endocardial sites. A data base of 38 characteristic mean integral maps was composed after visually selecting subgroups with nearly identical total QRS integral morphology and numerically evaluating intrasubgroup pattern uniformity and intersubgroup pattern variability. Corresponding endocardial pacing site locations were computed by a biplane cineradiographic method and outlined as segments on a standardized LV and RV polar projection. LV pacing resulted in 25 markedly different mean total QRS integral patterns, showing higher electrocardiographic sensitivity for anteroseptal (18 patterns) compared with posterolateral regions (seven patterns). RV pacing demonstrated 13 mean total QRS integral patterns, exhibiting less intersubgroup variation and comparatively low electrocardiographic sensitivity for the basal anterior and outflow regions. Comparison of LV with RV pacing revealed that QRS configurations produced at LV apical and LV midseptal sites closely resembled QRS configurations generated at RV apical, RV septal, and RV anterior sites, respectively. Total QRS time integral amplitudes showed considerable intrasubgroup variation but permitted global differentiation of spatially similar QRS patterns obtained during pacing at LV and RV sites. This study demonstrates that the QRS pattern of the total body surface electrocardiogram allows discrimination among 38 different LV and RV segments of ectopic endocardial impulse formation in patients with normal cardiac anatomy.

Autonomic pathophysiology in heart failure: carotid baroreceptor-cardiac reflexes

Abstract: We evaluated reflex cardiac responses mediated by carotid baroreceptors in 14 patients with treated congestive heart failure and 14 age-matched healthy subjects. We used a neck chamber to deliver two types of pressure change: 5 s of continuous 50-mmHg suction and an R wave triggered, ramped neck pressure-suction sequence. Reflex latencies (functions of baroreflex arc duration) were comparable in heart failure patients and healthy subjects. However, the average maximum baroreflex slope (gain) was less in heart failure patients than healthy subjects (2.0 vs. 3.5 ms/mmHg, P less than 0.010), the R-R interval response range was smaller (91 vs. 188 ms, P = 0.002), and the resting R-R interval position on stimulus-response relation (operational point) was significantly (13 vs. 40%, P = 0.001) closer to threshold. Stepwise regression analysis suggested that baseline R-R interval variability, used as an index of ongoing vagal-cardiac nerve traffic, and the inverse of antecubital vein plasma norepinephrine level, used as an index of sympathetic nerve activity, contributed significantly to the prediction of abnormal carotid baroreceptor-cardiac reflex responses. Thus our results suggest that in heart failure patients, carotid baroreceptor-cardiac reflex abnormalities are related significantly to ongoing abnormalities of vagal and sympathetic cardiovascular outflow.

Body surface mapping during percutaneous transluminal coronary angioplasty. QRS changes indicating regional myocardial conduction delay.

Abstract: Using a radiotransparent electrode array, body surface maps (BSMs) were constructed based on simultaneous recordings from 62 leads on the entire thorax before, during, and after balloon inflation during percutaneous transluminal coronary angioplasty (PTCA). Twenty-five patients were studied, and 30 angioplasties were performed; 20 patients had one-vessel disease, and five patients had two-vessel disease. In total, 15 dilations in the left anterior descending artery (LAD), seven in the right coronary artery (RCA), and eight in the left circumflex artery (LCx) were studied. For each patient, the BSM and the QRS integral map before, during, and after the inflation was compared by subtraction of recordings "during-minus-before" inflation and "before-minus-after" inflation. The subtraction was performed on the results of the QRS integral maps. The conclusions derived from the inspection of the BSMs and the difference maps show specific changes in the QRS complex during ischemia related to the corresponding ischemic segment in 21 of 25 patients in the three groups. An area of positive potentials remained present on the BSM during dilation, indicating a depolarization wave front. For the LAD group, positive potentials were seen on the anterior thorax and, for the RCA group, on the lower part of the thorax. By subtraction analysis, these changes were extracted and presented as difference maps. For the LCx group, the BSM revealed no changes in pattern but the difference map showed a difference vector pointing in a anteroposterior direction. A regional myocardial conduction delay was hypothesized as the most likely cause for the results.

Premature ventricular complex morphology. A marker for left ventricular structure and function.

Abstract: The shape of a premature ventricular complex (PVC) might reflect the presence or absence of myocardial disease. To test this, 100 patients with a PVC on a 12-lead electrocardiogram at cardiac catheterization or nuclear angiography were classified according to PVC morphology. Group 1 (n = 50) had PVC QRS complexes with either smooth and uninterrupted contour or with narrow (less than 40 msec) notching. Group 2 (n = 50) demonstrated PVC with broad (greater than or equal to 40 msec) notching or shelves. Clinical, electrocardiographic and angiographic variables were assessed to define group differences. All patients had one or more etiological forms of heart disease none of which distinguished either group. Groups 1 and 2 differed with respect to a history of congestive heart failure (12% vs. 66%, p = 0.0004), dilated cardiomyopathy (2% vs. 38%, p = 0.0005), and the presence of mitral regurgitation (13% vs. 58%, p = 0.001), respectively. In group 1, 45 of 50 (90%) patients with a PVC had no notching. Patients in group 2 had greater PVC QRS duration as compared with patients in group 1 (181 +/- 6 vs. 134 +/- 3 msec, p = 0.0001). End-diastolic volume index (EDVI) (78 +/- 3 vs. 139 +/- 11 ml/m2, p = 0.0000) and ejection fraction (EF) (0.59 +/- 0.02 vs. 0.34 +/- 0.03, p = 0.0000) significantly discriminated between group 1 and 2, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative analysis of ventricular late potentials in healthy subjects.

Abstract: Signal averaging is a technique that improves the signal-to-noise ratio. Obscuring random noise, it allows the detection of low-amplitude wave forms in the terminal portion of the QRS complex, also known as ventricular late potentials. A higher incidence of arrhythmic events has been found in patients with abnormal ventricular late potentials after an acute myocardial infarction. Few studies have been conducted in healthy subjects to assess normal values. Sixty-one healthy subjects were enrolled in our study (33 men and 28 women). The results (mean +/- standard deviation) are as follows: duration of the filtered QRS (QRS duration) was 95 +/- 10 ms; duration of the low-amplitude signals in the terminal portion of QRS less than 40 microV (LAS less than 40) was 32 +/- 8 ms; and root-mean-square voltage in the last 40 ms (RMS - 40) was 33 +/- 16 microV. A significant difference was noted in QRS duration between men and women (98 +/- 11 vs 92 +/- 6 ms, p = 0.006); no difference was found in LAS less than 40 (31 +/- 8 vs 34 +/- 8 ms) and in RMS-40 (36 +/- 17 vs 30 +/- 13 microV). QRS duration confidence limits of 95% were less than or equal to 114 ms for the total group, less than or equal to 120 ms for men and less than or equal to 104 ms for women. Normalization of QRS duration for height (normal value less than 66 ms/m) eliminated any difference between men and women.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal ECG waveform analysis should improve fetal surveillance in labour.

Abstract: Fetal heart rate (FHR) and fetal electrocardiogram (ECG) recordings were obtained from a scalp electrode with maternal thigh as reference and used for ST waveform analysis in 201 patients in labour. Nearly 45% had suspicious or abnormal FHR traces whilst only 27% had T/QRS ratio greater than 0.25 (mean +/- 2 SD). A normal T/QRS ratio identified 99.3% of fetuses with normal buffering capacity in cord artery blood. Of 13 infants with a cord artery blood pH less than 7.15, standard bicarbonate was less than 15.0 mmol/l in five who had an average T/QRS ratio less than 0.25 throughout labour. Of the eight with respiratory acidosis, five had an increase in T/QRS ratio greater than 0.25 for longer than 20 minutes prior to delivery, in two the ratio increased during the last few minutes and one had no change (pH 7.14). Persistent elevation of T/QRS in the first stage of labour identified those with decrease in buffer capacity in cord arterial blood (sensitivity of 94.1%). Acute hypoxia was recognized by the rapid rise in T/QRS. The specificity of T/QRS to identify fetuses at risk increased by combining the ST waveform analysis with FHR changes.

Late potentials and inducible ventricular tachycardia in surgically repaired congenital heart disease.

Abstract: We compared signal-averaged electrocardiography with invasive electrophysiological study in patients after surgical repair of congenital heart disease to determine if potentially useful correlations exist between the two methods for assessment of risk for ventricular tachycardia. Thirty-one patients (age, 1-49 years; mean, 10.6 years) with congenital heart disease repaired with right ventriculotomy or postrepair right bundle branch block (77% postoperative tetralogy of Fallot) who had electrophysiological study were studied with signal-averaged electrocardiography. Patients were classified by electrophysiological study results as having no inducible ventricular tachycardia, nonsustained ventricular tachycardia, or sustained ventricular tachycardia. Signal-averaged electrocardiograms were examined for the duration of low-amplitude (less than or equal to 40 microV) QRS signal, duration of total QRS, and root-mean-square voltage of the terminal 40 msec of the QRS. Low-amplitude terminal root-mean-square voltage of 100 microV or less had 91% sensitivity and 70% specificity for ventricular tachycardia inducible by electrophysiological study. Similar sensitivity but less specificity were seen using the criterion of 20 msec or more total low-amplitude QRS signal (initial plus terminal) or using total QRS duration of 128 msec or more. There was a weaker association between terminal low-amplitude QRS signal of 15 msec or more and inducible ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term electrocardiograph for screening

Abstract: An electrocardiograph has an R wave detector for detecting an R wave out of an electrocardiogram (ECG) signal being collected from a subject. When the R wave detector detects an R wave, a heart rate and an ST value of the ECG signal are written to a storage which is assigned to heart rates and ST values in synchronism with the R wave. When the subject presses an event switch on feeling a subjective symptom, the waveform of the ECG signal is written to another storage which is assigned to waveforms. The electrocardiograph records a minimum necessary amount of information for screening, i.e., the heart rates, ST values, and waveforms of ECG signal associated with subjective symptoms. The electrocardiograph is, therefore, miniature and easy to carry while reducing the period of time necessary for analysis.

Anatomic validation of electrocardiographic estimation of the size of acute or healed myocardial infarcts

Abstract: Seventeen new criteria added to the simplified version of the Selvester QRS scoring system to comprise the complete version were evaluated to determine their value in estimating the size of single infarcts. These non-Q-wave criteria might be particularly useful regarding posterolateral infarcts in the distribution of the left circumflex artery. The study population was made up of 21 anterior, 30 inferior and 20 posterolateral single myocardial infarction (MI) patients with no evidences of bundle branch or fasccular blocks, ventricular hypertrophy or previous MI on their final stable electrocardiogram. The complete system's maximum 32 points is capable of indicating MI in 96% of the left ventricle and it estimated a mean electrocardiographic MI size that better approximated the anatomic size compared with the simplified version in all Ml locations. The correlation between anatomic and electrocardiographic MI size using the complete system was better and statistically significant for the posterolateral MI group (simplified r = 0.55, p 1 and ≤0.4 mV in V 2 were particularly helpful. This study documents the improved ability provided by the 17 additional non-Q-wave criteria which have been added in the complete version of this scoring system regarding the sizing of infarcts in the region of the left ventricle supplied by the left circumflex artery.

Lack of correlation between transient myocardial ischemia and late potentials on the signal-averaged electrocardiogram.

Abstract: The relation between transient myocardial ischemia and late potentials was investigated in 100 patients with coronary artery disease who underwent serial recordings of the signal-averaged electrocardiogram before, during and after dipyridamole infusion. During this test, 47 patients (group 1) developed transient myocardial ischemia (with ST elevation in 14 cases and ST depression in 33), whereas 53 patients (group 2) did not. Baseline signal-averaged electrocardiogram was abnormal in 20 patients (20%): a QRS duration >115 ms was seen in 6 patients, a late potential (root mean square voltage of last 40 ms of QRS [RMS40]

Top-resolution frequency analysis of electrocardiogram with adaptive frequency determination. Identification of late potentials in patients with coronary artery disease.

Abstract: Frequency analysis of the electrocardiogram with Fourier transform is a sensitive method of detecting late potentials. However, information about localization of late potentials is lost, frequency resolution is poor, and window functions have to be applied. We therefore analyzed multiple segments (25 msec long) of the surface electrocardiogram ("spectrotemporal mapping") with adaptive frequency determination (AFD), an autoregressive algorithm that is characterized by high-frequency resolution in very short segments without the use of window functions. Results were compared with those from Fourier transform and the Simson method. We studied 38 patients after myocardial infarction (MI) with sustained ventricular tachycardia (VT), 21 patients after MI without VT, and 18 healthy subjects. Frequency peaks could be clearly differentiated until a minimal interval of 6 Hz; with fast Fourier transform (Blackman Harris window) in a much longer segment (80 msec), the spectral peaks merged into one another at an interval of about 30 Hz. AFD revealed high-frequency components as narrow peaks in the range of 40-160 Hz in 28 of 38 patients (74%) after MI with VT. Because of the short segment size, exact localization of late potentials was possible; in most of the patients, the peaks occurred in segments inside the QRS complex and ended 20 +/- 10 msec after termination of the QRS complex. In patients after MI without VT, only four of 21 patients (19%) had spectral peaks in segments after the end of the QRS complex; however, 13 of 21 patients demonstrated microvolt potentials in segments within the QRS complex. These potentials did not extend beyond the end of normal ventricular activation. Only two of 18 healthy subjects showed abnormal AFD results. Patients with bundle branch block did not need to be excluded. AFD allowed good differentiation between late potentials and noise by a characteristic pattern of the spectral peaks. For the Simson method, patients with bundle branch block had to be excluded, and overall sensitivity was 42%. In five cases, the cause of failure of the Simson method could be identified as incorrect determination of the QRS limits due to noise. Thus, AFD is a promising method for detailed analysis of late potentials; it combines the advantages of frequency analysis (good differentiation between signal and noise and high-pass filters not necessary) and time domain analysis (localization of late potentials).

Prognostic use of a QRS scoring system after hospital discharge for initial acute myocardial infarction in the Framingham cohort.

Abstract: Myocardial infarct size is an important risk factor for survival after acute myocardial infarction (AMI). The purpose of this study was to determine the prognostic value of myocardial infarct size, as estimated by the Selvester 54-criteria/32-point QRS scoring system, in the Framingham cohort. During the first 30 years of the Framingham Heart Study, a total of 384 participants developed an AMI requiring hospitalization; from this group, 243 patients met the following inclusion criteria: (1) no electrocardiographic changes due to a previous infarction, (2) survival >3 days after discharge from the AMI hospitalization and (3) no electrocardiographic evidence of conduction disturbances or ventricular hypertrophy at the time of their final inhospital electrocardiogram. Univariate and multivariate analyses were performed to test the association of the QRS score, and other associated risk factors, with time until coronary heart diseaserelated death. QRS score was found to be significantly associated with outcome (p = 0.03), as was the systolic blood pressure before infarction (p >0.001). Both univariate and multivariate analysis showed that a history of systolic hypertension was the variable most strongly associated with coronary heart disease-related death. Thus, identification of AMI survivors at high risk for subsequent mortality can be improved by routine blood pressure measurement before AMI, and QRS scoring of the electrocardiogram taken at hospital discharge.

Simultaneous QRS detection and feature extraction using simple matched filter basis functions

Abstract: A simple, easily implemented method is presented for extracting from an electrocardiogram (ECG) features describing QRS morphology. Tests using the American Heart Association (AHA) database indicate that these features are successful at enabling premature ventricular contractions (PVCs) to be associated with other PVCs on the basis of morphology 99% of the time. The good performance of this method suggests that basis functions for separating signal from noise in QRS complexes need not be highly detailed and that a concise description of QRS morphology in terms of 4 numbers is adequate for distinguishing normal QRSs from PVCs. The method of calculating features continually from ECG data makes clearer the role of window alignment in QRS feature extraction. The simplicity and effectiveness of the method should make it useful to researchers. >

The effects of pacing-induced left bundle branch block on left ventricular systolic and diastolic performances.

Abstract: To assess the effects of pacing-induced left bundle branch block on left ventricular (LV) systolic and diastolic performance, we performed digital subtraction ventriculography while simultaneously measuring LV pressure with a catheter tip micromanometer. The subjects included 10 patients with a sinus rhythm, a normal QRS duration and PR interval within 0.22 sec. LV performance was assessed during both right atrial pacing (AP) and atrioventricular sequential pacing (AVP) at the same pacing rate. The atrioventricular pacing interval during AVP was adjusted to be the maximal interval that showed the QRS configuration seen during complete right ventricular pacing. LV end-diastolic pressure and volume during AVP did not differ from those during AP. Peak positive and negative dp/dt during AVP were significantly lower than those during AP. Time constants were also significantly longer during AVP. The QRS duration during AVP significantly correlated with end-systolic volume and time constants, and inversely correlated with ejection fraction and +dp/dt. These observations indicated that conduction disturbance per se, induced by AVP, could not only impair LV systolic performance but also diastolic performance, possibly due to asynchronous contraction and relaxation of the left ventricle.