T-wave alternans poorly prognostic in primary prophylactic ICD patients: a prospective EU-CERT-ICD study

Background

New methods to identify patients who truly benefit from primary prophylactic implantable cardioverter defibrillation (ICD) are urgently needed. T-wave alternans (TWA) represents a beat-to-beat fluctuation in the morphology of the ST-segment and T-wave. It has been shown to associate with arrhythmogenesis of heart and sudden cardiac death [1]. We hypothised that TWA might associate with benefit from ICD implantation in primary prevention.

Methods

In EU-CERT-ICD study, we prospectively enrolled 2327 primary prophylactic ICD candidates from 15 European countries. A 24-hours Holter-monitoring was taken from all recruited patients at enrolment. TWA was assessed from Holter-monitoring using MMA method with Getemed Cardioday software. To assess the benefit from ICD treatment, we used outcomes all-cause mortality, appropriate shock and survival benefit. We conducted Cox regression model, competing risk regression model and propensity score adjusted Cox regression model. TWA was assessed both as contiguous variable and with cut-off points <47 μV and <60 μV.

Results

Final cohort included 1,734 valid T-wave alternans samples, 1,211 patients with ICD and 523 control patients with conservative treatment, with mean follow-up time 2.3 years. TWA <60 μV predicted lower all-cause mortality in ICD patients in univariate cox regression model (HR 1.484, 95% CI 1.024–2.151, p=0.0374). In multivariate models, TWA did not predict death or appropriate shocks in ICD patients. In addition, TWA did not predict death in control patients. In propensity score adjusted Cox regression model, TWA did not predict ICD benefit.

Conclusion

T-wave alternans is poorly prognostic in primary prophylactic ICD patients. Altough it may predict life-threatening arrhythmias and sudden cardiac death in several patient populations, it cannot be used in assessing benefit from implantable cardioverter defibrillator in primary prevention among patients with ejection fraction ≤35%.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Community's 7th Framework Program FP7/2007-2013

3254Manifestations of myocardial fibrosis in the standard 12-lead electrocardiogram

Background

Myocardial fibrosis has substantial role in sudden cardiac deaths (SCD). Major challenge in preventing SCDs is early recognition of vulnerable patients with fibrotic cardiomyopathy. Our aim was to find manifestations of myocardial fibrosis in 12-lead electrocardiogram (ECG).

Methods

Study population is based on the Fingesture study, which has gathered data from 5,869 consecutive autopsied SCD victims between 1998 and 2017 in Finland. The degree of fibrosis was determined based on the histological samples taken from the heart during autopsy and was categorized into four groups; 1) no fibrosis, 2) scattered mild fibrosis, 3) moderate patchy fibrosis and 4) substantial fibrosis. We were able to collect pre-mortem 12-lead ECGs from 1,100 SCD victims. Ischemic cardiomyopathy was the cause of death in 689 cases and 411 had nonischemic cardiomyopathy at autopsy in the group where ECG was available.

Results

Mean age of the study subjects was 66±13 years and 75% were male. At least some amount of myocardial fibrosis was present in 92% of the victims. QRS duration in ECG correlated with the degree of fibrosis in autopsy as follows; 96±21ms in group 1 (n=93), 97±20ms in group 2 (n=357), 103±26ms in group 3 (n=506) and 108±27ms in group 4 (n=144; p<0.001, β=0.153). Prevalence of fragmented QRS complex was higher among victims with severe fibrosis (40% in group 1, 43% in group 2, 60% in group 3 and 65% in group 4; p<0.001). Additionally, inferolateral T-wave inversions were more common in groups with increasing amount of myocardial fibrosis (5.4% in group 1, 13.2% in group 2, 20.4% in group 3 and 31.9% in group 4; p<0.001). Associations were visible in both ischemic and nonischemic SCDs but reached statistical significance only among ischemic SCD victims. Heart rate corrected JT interval and Sokolow-Lyon index had no linear correlation with the degree of fibrosis.

Conclusions

Myocardial fibrosis was associated with QRS prolongation, T-wave inversions and QRS fragmentation among SCD victims. Fibrosis did not manifest as clearly in ECG among patients with nonischemic cardiomyopathies as among ischemic SCD victims. The results may explain the increased risk for SCD in patients with abnormal QRS complex or inverted T waves providing means for recognizing patients with underlying fibrotic cardiomyopathy.

Acknowledgement/Funding

Sigrid Juselius Foundation, Foundation of Cardiac Research, Paavo Nurmi Foundation and Paulo foundation, Finland

Effects of noise and filtering on SVD-based morphological parameters of the T wave in the ECG

Singular value decomposition (SVD) based electrocardiogram (ECG) morphology analysis is a novel method in the assessment of subtle abnormalities in the T wave morphology of 12-lead ECG. As various types of noise contaminate the ECG signal and create a bias for the morphological analyses, this study was designed to estimate the effects of noise on the SVD method in an experimental setup. Ideal signals were generated by filtering real ECG signals several times with the Savitzky-Golay filter. Random and real noise samples were superimposed on the ideal signals. The noisy signals were filtered with a power line interference filter combined with the Savitzky-Golay or the wavelet filter. Results show that noise increased both the dipolar and non-dipolar components significantly unless filtering was applied. R-TWR (relative T wave residuum) and A-TWR (absolute T wave residuum) were four to eight times higher in noisy signals. The experiments with patient data demonstrated that certain types of noise may even lead to erroneous classification of patients. Filtering brings the median values closer to the correct ones and decreases significantly the variance of the values of parameters.

Causes of death in pedigrees with the 3243A>G mutation in mitochondrial DNA

BACKGROUND

Causes of death of patients with the 3243A>G mutation have been described in case reports or case series with a limited number of subjects.

METHODS

Eighty-two maternally related sibships of 11 families with 3243A>G were included in this survey. The lifespan of each subject in these families was compared with the life expectancy of the general population, adjusted with respect to year of birth and gender. Causes of death were determined among 3243A>G carriers and their first-degree maternal relatives.

RESULTS

We identified 123 deceased subjects in families with 3243A>G and found an excess mortality during the early years of life and young adulthood. The median age at death for 3243A>G carriers and their first-degree maternal relatives was significantly lower than that of the general population. Neurological and cardiovascular diseases made up one-third of the causes of death. Sudden and unexpected death was not uncommon in patients with cardiovascular diseases, diabetes and epilepsy.

CONCLUSIONS

3243A>G carriers and their first-degree maternal relatives died younger than was predicted by their life expectancy at birth. Neurological disease was the most common cause of death.

Increased pulse pressure is associated with reduced baroreflex sensitivity

Although pulse pressure (PP), heart rate variability (HRV) and baroreflex sensitivity (BRS) have been shown to predict cardiovascular events and mortality in various populations, their relationships have not been clarified. We examined these associations in two separate population-based samples of healthy middle-aged subjects. In population 1, data were obtained from 149 subjects (71 men and 78 women) aged 35-64 (mean 47.7) years, and in population 2, from 214 subjects (88 men and 126 women) aged 40-62 (mean 50.5) years. Increased 24-h ambulatory PP was related to decreased cross-spectral BRS independent of age and gender (beta=-0.28, P<0.001 for population 1; beta=-0.22, P=0.003 for population 2). This association remained significant when 24-h ambulatory diastolic blood pressure, body mass index, smoking and alcohol intake were added as covariates in the multivariate analysis. Increased ambulatory PP was also associated with increased beat-to-beat systolic arterial pressure variability. Associations between ambulatory PP and HRV were not significant after controlling for age and gender. Our results suggest that elevated PP does not affect overall HRV, but it interferes with baroreflex-mediated control of the heart rate. This association may be due to a common denominator, such as arterial stiffness, for PP and BRS.

Dynamics of the uncorrected QT interval during vagal-induced lengthening of RR intervals

Analysis of 21 episodes of vagal-induced atrioventricular block showed that the uncorrected QT intervals at the end of the corresponding RR pauses were not prolonged, in reference to the pre-block QT intervals, with pauses shorter than 1,280 ms. Subsequently, they gradually lengthened as the RR pauses progressively increased to 13,710 ms. This dynamic behavior of the QT interval in subjects without structural heart disease could have resulted from a complex interaction between the cumulative effects of previous cycle lengths (memory effect?) and the autonomic nervous system.

Effect of stored electrograms on management in the paced patient

Advances in modern pacemaker technology offer possibilities to diagnose asymptomatic arrhythmias and to document the causal relation between symptoms and infrequently occurring arrhythmias. Diagnostic and memory functions of pacemakers allow both the automatic detection of arrhythmias and retrieval of stored electrograms of the arrhythmia episodes. Asymptomatic episodes of atrial fibrillation (AF), sustained ventricular tachycardia (VT), and nonsustained VT of the patients with impaired left ventricular function may have real clinical importance in pacemaker patients. Recognition of these arrhythmias may result in changes in the treatment of the patients, such as anticoagulation of patients with episodes of paroxysmal AF, and therapy guided by electrophysiologic testing of patients with nonsustained or sustained VT. Stored electrograms may also help in defining whether the symptoms experienced by pacemaker patients are due to arrhythmias. Improvements in the arrhythmia detection algorithms and memory functions will still be needed in the future to reliably detect the occurrence of various arrhythmias in pacemaker patients. After these improvements, the diagnostic features of pacemakers should offer a unique opportunity to further improve the clinical management of pacemaker patients.

Controlled 5-mo aerobic training improves heart rate but not heart rate variability or baroreflex sensitivity

Endurance-trained athletes have increased heart rate variability (HRV), but it is not known whether exercise training improves the HRV and baroreflex sensitivity (BRS) in sedentary persons. We compared the effects of low- and high-intensity endurance training on resting heart rate, HRV, and BRS. The maximal oxygen uptake and endurance time increased significantly in the high-intensity group compared with the control group. Heart rate did not change significantly in the low-intensity group but decreased significantly in the high-intensity group (-6 beats/min, 95% confidence interval; -10 to -1 beats/min, exercise vs. control). No significant changes occurred in either the time or frequency domain measures of HRV or BRS in either of the exercise groups. Exercise training was not able to modify the cardiac vagal outflow in sedentary, middle-aged persons.

Similar effect of revascularization on technetium-99m( )sestamibi and 15-(p-iodophenyl)pentadecanoic acid uptake in myocardial infarction patients

To study its usefulness as a tracer for assessment of the perfusion and viability of myocardium, 15-(p-iodophenyl)pentadecanoic acid (IPPA) was compared with technetium-99m sestamibi (MIBI). Dual-tracer single-photon emission tomography rest imaging was performed no more than 2 months before and 3 months after coronary artery bypass grafting in 28 patients with previous anterior (n=13) or inferior (n=15) infarction. The size of MIBI and IPPA defects decreased from 14%+/-12% and 13%+/-9% to 10%+/-11% and 9%+/-7%, respectively (P<0.001 for both). The MIBI uptake increased in the infarct zones from 35%+/-11% to 43%+/-8% (P<0.001), and in the peri-infarct zones from 50%+/-11% to 55%+/-10% (P<0.05). The IPPA uptake increased in the infarct zones from 37%+/-11% to 44%+/-13% (P<0.001), and in the peri-infarct zones from 51%+/-11% to 57%+/-12% (P<0.05). In nine patients with improved regional echocardiographic wall motion score after bypass surgery, the pre-operative uptake values of both MIBI and IPPA in the infarct and peri-infarct zones were on average slightly but not significantly higher than in 19 patients with no observed improvement in regional wall motion score. In patients with improved regional wall motion, the MIBI scans and the IPPA scans showed (non-significant) decreases in defect size and increases in infarct and peri-infarct zone uptake after bypass surgery. Similar (in some cases significant) changes were observed in the patients without improvement in wall motion. Thus IPPA and MIBI provided similar information about perfusion and viability in pre- and postoperative evaluation of patients with clinically evident myocardial infarction and with normal global ejection fraction. Regardless of the tracer used, the resolution capability of the dual-tracer method with a rest imaging protocol was not sufficient to differentiate viable from non-viable infarction defects in unselected individual patients with a normal ejection fraction.

Muscarinic receptor stimulation with edrophonium hydrochloride does not elevate ventricular fibrillation thresholds in humans

INTRODUCTION

Although decreased vagal tone, as measured by heart rate variability is a risk factor for ventricular fibrillation (VF) and sudden cardiac death, it is unknown whether increasing vagal tone has an antiarrhythmic effect. The purpose of this study was to determine whether edrophonium hydrochloride (HCI), a vagomimetic agent, increases VF threshold.

METHODS AND RESULTS

Twenty-eight consecutive patients with previously implanted defibrillators had two inductions of VF by monophasic direct-current shocks delivered at 10 to 30 msec after the T wave peak, escalating energies (0.4, 1, then 3 J) until VF was induced. If VF was not induced, this protocol was repeated at the T wave peak and then at 10 to 30 msec before the T wave until VF was induced. Patients were randomized to receive edrophonium HCl (12 to 18 mg) or no drug before repeating the protocol for the second VF induction. The mean sinus cycle length increased from 782 to 872 msec in the group receiving edrophonium HCI (P = 0.006 ). In the control group, the mean sinus cycle length remained unchanged (838 vs 858 msec). The mean energy to induce VF, coupling interval relative to the T wave, and the number of attempts to induce VF were not different between VF induction attempts 1 and 2, and they were not different between the group receiving edrophonium HCl and the control group.

CONCLUSION

In a sedated patient population with implantable defibrillators, edrophonium HCI infusion prolongs sinus cycle length but does not change inducibility of VF using T wave shocks.

Accuracy of a novel real-time microprocessor QRS detector for heart rate variability assessment

Assessment of heart rate variability from 24-h recordings requires a high-quality Holter, expensive equipment and multistage processing of recordings. We compared a new personal computer-based digital QRS detector system with a Holter recorder, and found the two methods to be equally accurate in time and frequency domain measures of heart rate variability.

Heart rate variability in inappropriate sinus tachycardia

Analysis of heart rate variability in patients with inappropriate sinus tachycardia showed a 24-hour decrease in all temporal and spectral indexes, even after attempted correction to a rate of 75 beats/min. This may have resulted from a global decrease in parasympathetic activity or from a rapid sinus rate produced by other ill-defined mechanisms.

Repair of an aneurysm of the left main coronary artery

Coronary artery aneurysms are rare, especially in the left main coronary artery. Coronary artery aneurysms may rupture or cause myocardial infarction. There are only a few reports of coronary artery aneurysms of the left main coronary artery treated surgically. We report a case in which an arterial graft from the internal iliac (hypogastric) artery was used for the reconstruction of a congenital coronary artery aneurysm of the left main coronary artery. After a follow-up of 5 years, the patient is well and in good condition.

Hemodynamic recovery, atrial natriuretic peptide, and catecholamines during simulated ventricular tachycardia: effects of ventriculoatrial conduction

Ventriculoatrial (VA) sequence and neurohumoral responses may be important modulators of hemodynamic recovery during VT. We studied the effects of VA conduction on blood pressure recovery, and levels of atrial natriuretic peptide (ANP), epinephrine, and norepinephrine during simulated VT. After diagnostic coronary angiography, VT was simulated by rapid right ventricular pacing (150 beats/min, 3 mins) in a consecutive series of patients. Whenever the patients demonstrated VA dissociation during ventricular pacing, they were included in the study. After 10 minutes of recovery, a group of nine patients then underwent an additional VA pacing (150 beats/min, 3 mins, VA delay of 150 msec). Intra-arterial blood pressure was continuously monitored, and plasma ANP and catecholamine levels were measured before, during, and after both pacing protocols. The mean arterial pressures declined rapidly by 26% and 30% after initiation of ventricular and VA pacing, respectively. The blood pressure then gradually recovered, the hemodynamic recovery being better during VA pacing. Plasma ANP and catecholamine levels increased toward the end of both pacing periods. The observed increase in ANP concentration was more prominent during VA pacing than ventricular pacing (P < 0.001), whereas catecholamine levels increased similarly. The results show that during simulated VT hemodynamic recovery is partially dependent on VA sequence. The increases in circulating ANP and catecholamines occur too slowly to account for the rapid changes in blood pressures observed after initiation of simulated VT. Therefore, other mechanisms, such as reflex stimulation of the sympathoadrenergic nervous system, must be involved, too. ANP release increases when atrial contraction frequency increases, but the exact determinants for this release remain unknown.

Changes in myocardial energy metabolism in elective coronary angioplasty

STUDY OBJECTIVE

The aim was to investigate the effect of coronary angioplasty on myocardial energy metabolism, and to assure the safety of the procedure in patients with coronary heart disease.

DESIGN

Before angioplasty a catheter was introduced into the coronary sinus. Blood samples were taken simultaneously from femoral artery and coronary sinus before balloon inflation, upon balloon deflation, and two minutes later, and arteriovenous differences in myocardial substrates, pH, PCO2, oxygen saturation, and adenosine catabolites were determined.

PATIENTS

14 patients with angiographically documented coronary artery disease with lesions in the left coronary artery suitable for elective coronary angioplasty were included in the study.

RESULTS

During balloon inflation the positive femoroarterial-coronary sinus difference of lactate turned negative, from 0.21(SEM 0.05) mM to -0.10(0.11)mM, p less than 0.02. At the same time pH and PCO2 differences increased: from 0.04(0.00) U to 0.07(0.01) U, p less than 0.01, and from -1.15(0.10) kPa to -1.41(0.10) kPa, p less than 0.01, respectively. The changes were, however, transient and the arteriovenous differences in these metabolic variables rapidly returned towards preinflation levels after balloon deflation. The femoroarterial-coronary sinus concentration differences in glucose and free fatty acids became positive in coronary angioplasty. The energy state remained good during the procedure as assessed from the negligible net efflux of adenosine and its degradation products.

CONCLUSIONS

Elective coronary angioplasty can be performed without any persistent derangements in myocardial metabolism, and may in fact lead to improvement of utilisation of some myocardial substrates. Lactate appears to be a more sensitive indicator of short term ischaemia than adenosine degradation products.

Isometric exercise testing and echocardiography at rest in aortic valve incompetence

Thirty patients with aortic valve incompetence and 21 control subjects were examined by M-mode echocardiography at rest and radionuclide ventriculography during submaximal handgrip exercise. The patients had greater left ventricular dimensions and end-systolic wall stress values but peak systolic wall stress values did not differ. During exercise the controls' ejection fraction increased by 3 +/- 4%, 95% confidence interval (CI) from +1% to +5%, while the aortic incompetence patients showed no change -1% +/- 5%, CI from -3 to +1%. The 15 symptomatic aortic incompetence patients had a different ejection fraction response from the controls (-2 +/- 4%, p less than 0.01), CI from 4% to +1%, but the 15 asymptomatic patients had not (0 +/- 6%, not significant, CI from -3% to +3%). Three symptomatic and two asymptomatic patients with a decrease in ejection fraction below 5% during handgrip were not identified by left ventricular size and function of systolic loading conditions at rest. Neither echocardiographic or radionuclide parameters of left ventricular size and function at rest correlated with the individual ejection fraction changes during handgrip. Thus, in aortic valve incompetence, the radionuclide angiography assessed functional response to handgrip cannot be predicted by left ventricular size and function or systolic loading conditions at rest.

Reversal of proarrhythmic effects of flecainide acetate and encainide hydrochloride by propranolol

The use of membrane-active antiarrhythmic agents may be complicated by aggravation of existing arrhythmias or development of new drug-induced arrhythmias. Four patients, referred because of out-of-hospital cardiac arrest or symptomatic sustained ventricular tachycardia, were receiving class IC antiarrhythmic agents in an attempt to prevent inducibility of sustained ventricular tachycardia. New or worsening spontaneous arrhythmias developed while they were on flecainide acetate (n = 3) or encainide hydrochloride (n = 1) therapy. Spontaneous runs of rapid nonsustained and sustained ventricular tachycardia developed in two. Increased frequency of premature ventricular contractions and repetitive forms of ventricular ectopic activity developed in one, despite the fact that inducibility of sustained ventricular tachycardia had been prevented. Salvos and nonsustained ventricular tachycardia developed in the fourth patient. Propranolol had failed to prevent inducibility of sustained ventricular tachycardia during previous programmed stimulation studies in three of the four patients, but it reproducibly suppressed drug-induced arrhythmias that appeared only after administration of the IC agents in each patient. Suppression of the proarrhythmic effects by beta-adrenergic blockade suggests a possible interaction of these drugs with autonomic function in the genesis of the observed proarrhythmic effects. Direct pharmacologic control of proarrhythmic drug effects has not previously been reported.

Theophylline and salbutamol in combination in patients with obstructive pulmonary disease and concurrent heart disease: effect on cardiac arrhythmias

We compared the frequency and severity of cardiac arrhythmias during combined oral theophylline and inhaled salbutamol vs. salbutamol therapy alone in 18 patients with moderate to severe chronic obstructive pulmonary disease who had concurrent cardiac disease. Seventeen patients showed at least one supraventricular premature complex (SVPC) on the 24-h ECG recording when receiving salbutamol alone: eight patients had isolated SVPCs, less than 10/h; five patients had greater than or equal to 10 SVPCs/h; eight patients showed runs of supraventricular tachycardia or paroxysmal atrial fibrillation. Seventeen patients also had at least one ventricular premature complex: seven patients had less than 10 isolated PVCs/h, five patients greater than or equal to 10 PVCs/h; eight patients had paired or multifocal PVCs and one patient a run of ventricular tachycardia. The addition of oral theophylline at an average dose of 600 mg in the evening (blood concentrations showed a mean maximum of 13.4 +/- 4.0 (SD) and minimum of 5.5 +/- 2.9 mg/l) had no influence on the frequency or severity of either ventricular or supraventricular arrhythmias. Thus, cardiac arrhythmias are very common in patients with chronic obstructive pulmonary disease and concomitant heart disease, but oral theophylline added to a regimen of salbutamol does not seem to affect the occurrence or severity of arrhythmias.

Left ventricular dimensions during isometric exercise in aortic valve incompetence assessed by M-mode echocardiography and gated equilibrium radionuclide angiography

We compared M-mode echocardiographic and gated equilibrium radionuclide angiography assessment of the left ventricular (LV) dimensions at rest and during isometric exercise in 18 patients with chronic aortic valve incompetence. The two methods showed a satisfactory correlation when comparing LV size at rest and during exercise (LV end-diastolic dimension in echocardiography vs LV end-diastolic volume in radionuclide angiography, r = 0.80, P less than 0.01 at rest and r = 0.81, P less than 0.01 at rest and r = 0.75; P less than 0.01 during exercise), but fractional shortening in echocardiography and ejection fraction in radionuclide angiography did not correlate (r = 0.27, not significant (NS) at rest and r = 0.34, NS during exercise). Thus echocardiography and radionuclide angiography describe LV dimensions at rest and during handgrip exercise in a similar fashion, documenting the concordance of these noninvasive methods to describe LV size in aortic incompetence at rest and during exercise.

Cellular electrophysiological changes during ischemia in isolated, coronary-perfused cat ventricle with healed myocardial infarction

Cellular electrophysiological consequences of acute ischemia superimposed on healed myocardial infarction were studied in isolated, coronary-perfused cat left ventricles 2-4 months after ligation of multiple distal tributaries of the left anterior descending and circumflex coronary arteries. Oxygenated Tyrode's solution was perfused through the left anterior descending and circumflex coronary arteries, and the preparations were superfused with Tyrode's solution gassed with 95% N2-5% CO2. Transmembrane action potentials were recorded from the endocardial cells in normal and infarcted zones. There were no significant differences in measured action potential variables and refractory periods between cells in the normal and infarcted zones before acute ischemia. When coronary perfusion was discontinued ("ischemia"), resting potential, action potential amplitude, and action potential duration were reduced, and the refractory period was shortened progressively in cells of the normal zone. However, the action potential changes were less prominent, and the refractory period was unchanged in cells in the infarcted zone. As a result, there were significant differences in resting membrane potential, action potential amplitude, action potential duration, and refractory period between cells in the normal and infarcted zones at 10 minutes of ischemia. These differences became larger as the ischemic period was prolonged. Spontaneous rapid ventricular activity was observed during the last 20-30 minutes of ischemia in four of eight preparations with healed myocardial infarction, whereas no spontaneous rapid ventricular activity was recorded in any of six normal heart preparations. Our data suggest that superimposition of acute ischemia on healed myocardial infarction produces electrophysiological inhomogeneities that may enhance arrhythmogenesis.

Disopyramide pharmacokinetics in patients with acute myocardial infarction

To study the effects of acute myocardial infarction on the pharmacokinetics of disopyramide a single oral dose of disopyramide base (200 mg) was administered to 6 patients with myocardial infarction both in the acute (Study I) and recovery (Study II) phases. An intravenous tracer dose of 14C-disopyramide (2.5 micrograms/0.3 mg) was given simultaneously with the oral dose. On the basis of the intravenous tracer data, the volume of distribution, binding to plasma proteins, total plasma clearance, renal clearance and elimination half-life of disopyramide and mono-N-dealkyl disopyramide were the same in Studies I and II. The peak serum concentrations of disopyramide after oral dosing in Studies I and II were 2.6 +/- 1.2 (SEM) and 6.4 +/- 1.9 microgram/ml, respectively (p less than 0.05), the peak times 3.29 +/- 1.22 and 1.21 +/- 0.39 h (N.S.) and the AUCINF 38.0 +/- 7.7 and 60.7 +/- 9.9 micrograms . h . ml-1 (p less than 0.05). The recovery of disopyramide in urine over 3 days averaged 46% and 47% of dose, and that of mono-N-dealkyl disopyramide 22% and 16% of the dose, respectively. Thus, the gastrointestinal absorption of disopyramide was disturbed, resulting in low plasma concentrations after oral dosing, whereas the elimination of disopyramide was unaltered in the acute phase of myocardial infarction.