Analysis of the spontaneous variability of ventricular arrhythmias: consecutive ambulatory electrocardiographic recordings of ventricular tachycardia

Outcomes of Patients Who Have Incidental Non-Sustained Ventricular Tachycardia Identified on Cardiac Implantable Electronic Device Interrogation

Background: Non-sustained ventricular tachycardia (NSVT) is an arrhythmia prevalent in both structurally normal and abnormal hearts. Methods: We conducted a single-center retrospective clinical audit of patients followed-up in a device clinic with one or more incidental NSVT episodes recorded on their device between November 2017 and August 2018 and followed up patients for outcomes until January 2019. Results: A total of 83 patients were included in the analysis with one or more episodes of NSVT on device interrogation. Those identified to have NSVT were more likely to be male (74.7%) and there was a mean of 14.2 beats per episode and a mean of 3.7 episodes for each patient. Only 24.7% of patients had electrolytes checked within 4 weeks of episode detection and 18.3% had an echocardiogram post-episode. The majority of patients (73.5%) were followed up again in the pacing clinic but had no changes in medication, or other management implemented. In terms of outcomes, 81.7% of patients had no admission to hospital, mortality, or shock during the follow-up period. Conclusions: Most patients who developed NSVT did not have an extra follow-up, medication review, or investigation. Despite this, outcomes such as admission, shock, or death were uncommon.

Ventricular arrhythmias are not a short-term reproducible phenomenon--why long recording monitoring is necessary

BACKGROUND

The variability of ventricular arrhythmias (VA) among different days of the week is not well detected by one-day Holter monitoring.

AIMS

To evaluate whether there are differences in VA distribution pattern during long recording period.

METHODS

The EKG was recorded for 14 h per day during 7 days by Holter system in 34 consecutive pat ventricular couplets and non-sustained ventricular tachycardia (NSVT) recording from patients provided graphic data. We applied the Hurst method (H Coefficient) which evaluates whether a repetitive phenomenon is random or not. When the H is >0.5 and <1 means it is not random and implies a long-term memory effect. Considering the arrhythmic variability, the data were also analyzed by repetitive ANOVA comparing incidence of arrhythmias among the days.

RESULTS

Isolated PVCs and ventricular couplets during 98 h recording provided graphic of the occurrence. A trend of increasing and decreasing of arrhythmias was observed which looks erratic. The H coefficient, however, was significantly >0.5 for all patients. Repeated ANOVA showed statistic difference among days in 31 patients with isolated PVCs; in 26 with ventricular couplets and 19 with NSVT when analyzed per hour during week days (p < 0.05).

CONCLUSION

PVCs, ventricular couplets and NSVT are not a random phenomenon. Our data suggest the occurrence of ventricular arrhythmias had no similarity among the days, making unlikely that a single Holter recording for 24h may capture this phenomenon.

Evaluation of ventricular arrhythmias in early clinical pharmacology trials and potential consequences for later development

This white paper, prepared by members of the Cardiac Safety Research Consortium, discusses several important issues regarding the evaluation of ventricular arrhythmias in early clinical pharmacology trials and their potential consequences for later clinical drug development. Ventricular arrhythmias are infrequent but potentially important medical events whose occurrence in early clinical pharmacology trials can dramatically increase safety concerns. Given the increasing concern with all potential safety signals and the resultant more extensive electrocardiographic monitoring of subjects participating in early phase trials, an important question must be addressed: Are relatively more frequent observations of ventricular arrhythmias related simply to more extensive monitoring, or are they genuinely related to the drug under development? The discussions in this paper provide current thinking and suggestions for addressing this question.

[Holter monitoring and programmed ventricular stimulation]

Long-term ECG recordings are the method of choice to evaluate quantity and quality of spontaneous rhythm disturbances. However, this method is limited by the variability of the arrhythmias. Invasive procedures such as programmed stimulation allow the provocation of tachyarrhythmias. Indications for both methods are diagnostic clarification of clinical symptoms, risk stratification with respect to arrhythmogenic sudden cardiac death as well as the control of antiarrhythmic therapy.Due to the high variability of spontaneous complex ventricular arrhythmias, Holter monitoring often fails to document the cause of severe symptoms such as syncope or sudden cardiac death. In these patients, invasive electrophysiological testing is required to provoke the arrhythmia.The prognostic significance of spontaneous ventricular arrhythmias recorded during ambulatory monitoring depends on the underlying cardiac disease. In patients with coronary artery disease and a history of myocardial infarction there is evidence that frequent single and/or complex ventricular extrasystoles indicate an increased risk of sudden cardiac death, especially in the presence of a reduced left ventricular function. In these patients, programmed ventricular stimulation can further characterize a highrisk group.For the management of antiarrhythmic therapy in symptomatic patients, under certain conditions both methods appear to be helpful. For the majority of these patients, however, the invasive electrophysiologic study should be preferred.Thus, long-term ECG recordings and programmed electrical stimulation are no competing, but complementary methods in clinical cardiology.

Reproducibility of drug efficacy predictions by Holter monitoring in the electrophysiologic study versus electrocardiographic monitoring (ESVEM) trial. ESVEM Investigators

Selection of antiarrhythmic therapy may be based on suppression of spontaneous ventricular arrhythmias assessed by Holter monitoring, but the implications of discordant Holter results on repeat 24-hour monitoring has not been defined. This study examines the frequency and significance of reproducible Holter suppression on two 24-hour recordings in the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial. Repeat 24-hour Holter monitoring was obtained in patients randomized to the Holter monitor limb of the ESVEM trial, during the same hospitalization, after a drug efficacy prediction. These Holters were not used to define drug efficacy but were subsequently analyzed to determine the reproducibility of drug efficacy predictions by Holter monitoring. A repeat 24-hour Holter monitor, following the one that predicted drug efficacy, was available in 119 patients. Ninety-nine patients (83%) also had suppression that met efficacy criteria on the second Holter monitor. There were no significant differences in arrhythmia recurrence (p = 0.612) or mortality (p = 0.638) in patients with concordant Holter results (n = 99; 1-year arrhythmia recurrence = 45%; 1-year mortality = 10%) compared with those with discordant Holter results (n = 20; 1-year arrhythmia recurrence = 45%; 1-year mortality = 16%). We conclude that (1) there is discordance between the first effective Holter monitor and a repeat Holter monitor in 17% of patients, and (2) suppression of ventricular ectopic activity on 2 separate 24-hour Holter monitors does not identify a group with a better outcome, nor does failure of suppression on the second Holter monitor identify a group with a worse prognosis.

Long-term temporal patterns of ventricular tachyarrhythmias

BACKGROUND

Technological limitations have precluded investigation of long-term temporal patterns of ventricular tachyarrhythmia recurrences. Newer implantable cardioverter-defibrillators permit such analyses by accurately recording the time and date of tachycardia detections during long-term follow-up. This study tests the hypothesis that ventricular tachycardia occurrences are randomly distributed over time in individual patients.

METHODS AND RESULTS

The time and date of 727 episodes of ventricular tachyarrhythmias were recorded from the data logs of 31 patients with implantable cardioverter-defibrillators followed for a median of 177 days (range, 7 to 782 days). All patients had three or more ventricular tachycardia detections and no detections from causes other than ventricular arrhythmias. In 28 of 31 patients, the distribution of the interdetection time intervals during follow-up differed significantly (all P < .01) from an exponential model distribution of interdetection intervals that assumed that detections were equally likely to occur at any time during follow-up (random). The Kolmogorov-Smirnov goodness-of-fit test was used to compare sample and model distributions. In each patient, the nonrandom distributions resulted from a preponderance of interdetection time intervals that were shorter than predicted by the random model, resulting in a temporal clustering of arrhythmic events. The interdetection interval was < or = 1 hour and < or = 91 hours for 55% and 78% of all intervals, respectively. When only those episodes receiving shock or antitachycardia pacing therapy were analyzed, 25 of 29 patients still manifested nonrandom distributions (all P < .01). When only episodes with tachycardia rates > 240 beats per minute were analyzed, 11 of 13 patients manifested non-random distributions (all P < .01).

CONCLUSIONS

Ventricular tachycardia detections and delivered antitachycardia therapies by implantable cardioverter-defibrillators are nonrandomly distributed throughout long-term follow-up in the majority of patients. The temporal clustering of these arrhythmic events may allow preemptive antiarrhythmic therapy and should be considered in the design of therapy based on suppression of spontaneous ventricular arrhythmias to statistically derived end points.

Prognosis of asymptomatic patients with hypertrophic cardiomyopathy and nonsustained ventricular tachycardia

BACKGROUND

In the early 1980s, studies performed in highly selected referral patients with hypertrophic cardiomyopathy reported a strong association between the presence of brief episodes of ventricular tachycardia (VT) on ambulatory ECG monitoring and sudden death. These observations led to antiarrhythmic treatment in many patients with hypertrophic cardiomyopathy and brief episodes of VT. In recent years, however, a growing awareness of the potential arrhythmogenic effects of antiarrhythmic medications has raised doubts regarding such a therapeutic approach, particularly in less selected and lower-risk patient populations.

METHODS AND RESULTS

In the present study, we examined the prognostic significance of nonsustained VT in a population of 151 patients with hypertrophic cardiomyopathy who were asymptomatic or had only mild symptoms at the time of their initial ambulatory ECG recording. Of the 151 study patients, 42 had episodes of VT and 109 did not. The runs of VT ranged from 3 to 19 beats, with 35 patients (83%) having < 10 beats. The number of runs of VT ranged from 1 to 12 in 24 hours, with 36 patients (86%) having < or = 5 episodes of VT. Thus, in most patients, the episodes of VT were brief and infrequent. Follow-up averaged 4.8 years. Of the 151 study patients, 6 died suddenly, 3 in the group with VT and 3 in the group without VT. Two other patients, both in the group without VT, died of congestive heart failure. The total cardiac mortality rate was 1.4% per year in the patients with VT (95% CI, 0.4% to 3.5%) and 0.9% in those without VT (95% CI, 0.4% to 2.0%; P = .43). The relative risk of cardiac death for patients with VT was 1.4 compared with patients without VT (95% CI, 0.6 to 6.1). The sudden death rate was 1.4% per year in the patients with VT (95% CI, 0.4% to 3.5%) and 0.6% in those without VT (95% CI, 0.2% to 1.5%; P = .24). The relative risk of sudden death for patients with VT compared with those without VT was 2.4 (95% CI, 0.5 to 11.9). Of the 151 patients included in the study, 88 (58%) remained asymptomatic and were not treated with cardioactive medications during follow-up. Of these 88 patients, 20 were in the group with VT and 68 in the group without VT. None of these patients died.

CONCLUSIONS

Our results show that cardiac mortality is low in patients with hypertrophic cardiomyopathy who are asymptomatic or only mildly symptomatic and have brief and infrequent episodes of VT on ambulatory ECG monitoring. Our findings also suggest that brief and infrequent episodes of VT should not be considered, per se, an indication for antiarrhythmic treatment in such patients.

Change of autonomic influence on the heart immediately before the onset of spontaneous idiopathic ventricular tachycardia

OBJECTIVES

This study aimed to assess heart rate variability immediately before the onset of episodes of spontaneous ventricular tachycardia.

BACKGROUND

It has been shown that decreased heart rate variability may be associated with a propensity to ventricular tachyarrhythmias. However, it is still disputed whether there is an abrupt change in heart rate variability immediately before the onset of these arrhythmias.

METHODS

Twenty-three patients with idiopathic ventricular tachycardia underwent two-channel 24-h Holter monitoring in a drug-free state. Spectral heart rate variability was computed as low (0.04 to 0.15 Hz) and high (0.15 to 0.40 Hz) frequency components at 2-min intervals over a 1-h period immediately before the onset of ventricular tachycardia. Average values of heart rate variability were also computed for the entire 24-h recordings. The low/high frequency component ratio was calculated as an index of the autonomic balance of the heart.

RESULTS

Seventy-one episodes of ventricular tachycardia from the 23 recordings formed this study. There was an increased low/high ratio during 6- to 8-min periods immediately before the onset of ventricular tachycardia episodes compared with the average values for the entire 24 h. This increase in the low/high ratio resulted largely from a decrease in the high frequency component value (4.70 +/- 1.15 vs. 5.10 +/- 1.06 ln[ms2] [mean +/- SD], p = 0.001) because there was no significant change in the low frequency component value (6.37 +/- 1.20 vs. 6.34 +/- 0.91 ln[ms2], p = 0.786, 95% confidence interval -0.25 to 0.19 ln[ms2], type II error < 0.0001 for change of 7.8%). In contrast, there were no significant differences in the low or high frequency components or low/high ratio between 6-min salvo-free periods 40 min before the onset of ventricular tachycardia and the average 24-h values (type II error < 0.0001, < 0.038 and < 0.1841, respectively, for change of 7.8%). The low/high ratio was also significantly higher during the 6 min immediately before the onset of ventricular tachycardia compared with that during the 6-min salvo-free periods 40 min before the onset of ventricular tachycardia. A significant increase in mean heart rate immediately before the onset of ventricular tachycardia was also noted.

CONCLUSIONS

There is a significant change in autonomic influence on the heart during the last few minutes preceding the onset of episodes of idiopathic ventricular tachycardia. This seems to result mainly from decreased vagal activity rather than enhanced sympathetic input to the heart.

Concentrated potassium chloride infusions in critically ill patients with hypokalemia

Although concentrated infusions of potassium chloride commonly are used to treat hypokalemia in intensive care unit patients, few studies have examined their effects on plasma potassium levels. Forty patients with hypokalemia were given infusions of 20 mmol of potassium chloride in 100 mL of normal saline over 1 hour; 26 patients received the infusions through the central vein and 14 patients through the peripheral vein. Plasma potassium ([K]p) was measured at 15-minute intervals during and after the infusion in 31 patients. delta K was defined as the difference between each potassium determination and baseline plasma potassium concentration. Continuous electrocardiographic recording was carried out during the infusion and during the 1-hour period immediately preceding the infusion. Mean baseline [K]p was 2.9 mmol/L and all subsequent plasma concentrations significantly increased from baseline. Mean peak [K]p was 3.5 mmol/L, [K]p (1 hour postinfusion) was 3.2 mmol/L, and mean postinfusion delta K was 0.48 mmol/L (range -0.1-1.7 mmol/L). Arrhythmias, changes in cardiac conduction intervals, and other complications did not occur. The frequency of premature ventricular beats decreased significantly during the infusion compared with that of the control period. The high concentration (200 mmol/L) and rate of delivery (20 mmol/hr) of the potassium chloride infusions were well tolerated, decreased the frequency of ventricular arrhythmias, and did not cause transient hyperkalemia.

Randomised trial of low-dose amiodarone in severe congestive heart failure. Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiaca en Argentina (GESICA)

In severe heart failure many deaths are sudden and are presumed to be due to ventricular arrhythmias. The GESICA trial evaluated the effect of low-dose amiodarone on two-year mortality in patients with severe heart failure. Our prospective multicentre trial included 516 patients on optimal standard treatment for heart failure. Patients were randomised to 300 mg/day amiodarone (260) or to standard treatment (256). Intention-to-treat analysis showed 87 deaths in the amiodarone group (33.5%) compared with 106 in the control group (41.4%) (risk reduction 28%; 95% CI 4%-45%; log rank test p = 0.024). There were reductions in both sudden death (risk reduction 27%; p = 0.16) and death due to progressive heart failure (risk reduction 23%; p = 0.16). Fewer patients in the amiodarone group died or were admitted to hospital due to worsening heart failure (119 versus 149 in the control group; risk reduction 31%; 95% CI 13-46%; p = 0.0024). The decrease in mortality and hospital admission was present in all subgroups examined and independent of the presence of non-sustained ventricular tachycardia. Side-effects were reported in 17 patients (6.1%); amiodarone was withdrawn in 12. Low-dose amiodarone proved to be an effective and reliable treatment, reducing mortality and hospital admission in patients with severe heart failure independently of the presence of complex ventricular arrhythmias.

Loss of efficacy during long-term cifenline therapy: development of antiarrhythmic resistance?

OBJECTIVE

To describe the possible development of antiarrhythmic resistance to cifenline, an investigational Class I agent.

METHODS

Forty patients with chronic ventricular premature depolarizations (VPDs) underwent dose-ranging studies with cifenline, an investigational Class I antiarrhythmic agent. Patients had a minimum of 30 VPDs/h detected by ambulatory electrocardiographic (ECG) monitoring over a 48-hour baseline placebo lead-in period. Twenty-two patients (55 percent) who initially responded received long-term cifenline therapy. Ambulatory ECG monitoring over 24 hours was repeated during active cifenline therapy at three-month intervals and during placebo reintroduction at six-month intervals.

RESULTS

After an average follow-up of 28 months, VPD frequency during cifenline therapy was similar to that during initial baseline placebo therapy in 8 of the 22 patients (36 percent) who initially responded. Placebo reintroduction following cifenline failure showed a VPD frequency similar to that with active therapy. All patients had further cifenline dosage increases without success. Plasma cifenline concentrations increased in all patients and were in the high therapeutic range. All 8 patients were switched to other Class I antiarrhythmic agents with successful VPD suppression during treatment with the first alternative drug.

CONCLUSIONS

We conclude that antiarrhythmic resistance occurred with cifenline in these patients as (1) initial efficacy was established for a minimum of two years, (2) VPD frequency was similar during cifenline therapy and placebo reintroduction, (3) cifenline therapy failure continued despite further dosage titration, and (4) alternative Class I antiarrhythmic therapy was successful in all patients. Repeat intermittent ambulatory ECG monitoring is necessary not only to assess the continued need for antiarrhythmic drug therapy, but also to establish continued long-term efficacy.

Effect of oral captopril on premature ventricular complexes in patients with preserved left ventricular systolic function: a randomized clinical trial

Some studies have suggested that angiotensin-converting enzyme (ACE) inhibition in patients with heart failure is associated with a decrease in frequency of spontaneous premature ventricular complexes (PVCs). It is not clear whether such a finding represents a primary effect of ACE inhibition or, instead, a secondary result of treatment of heart failure. For a primary drug effect to be present, PVC suppression during ACE inhibition should also occur in patients with preserved left ventricular systolic function. We therefore undertook a randomized double-blind placebo-controlled crossover clinical trial to assess the effect of oral captopril (50 mg. b.i.d.) on ventricular arrhythmia frequency in 11 patients with > 30 PVCs/h (during a 48-h ambulatory recording) and a left ventricular ejection fraction of > or = 45% (measured by radionuclide multigated acquisition scan). Pharmacologic activity of the administered drug was evidenced by an increase in median plasma renin activity to 2.4 ng/AI/ml/h from a value of 1.1 ng/AI/ml/h during placebo (p = 0.001) and an 8.5 +/- 10.3 drop in mean diastolic blood pressure during captopril versus placebo (p < 0.03). During captopril treatment, a mean of 491 +/- 378 PVCs/h were observed compared with 389 +/- 169 PVCs/h during placebo, a nonsignificant difference. There was also no significant change in left ventricular ejection fraction, plasma catecholamines, or serum potassium during captopril treatment. Thus, ACE inhibition in patients with preserved left ventricular systolic function fails to suppress ventricular ectopic activity. Extrapolated to patients with heart failure, our observations argue against a primary PVC suppressive action of ACE inhibitors but do not rule out possible secondary antiarrhythmic effects of these agents.

Incidence, pathophysiology and prognosis of exercise-induced sustained ventricular tachycardia associated with healed myocardial infarction

Of 150 consecutive patients with sustained monomorphic ventricular tachycardia (VT) (n = 116) or ventricular fibrillation (VF) (n = 34) late after acute myocardial infarction, 17 had reproduction of their sustained monomorphic VT during exercise testing. Data from these patients (group I) were compared with data from patients without exercise-induced VT (group II). No statistical difference was found between groups I and II with relation to age, sex, number of vessels with greater than 70% stenosis, left ventricular ejection fraction, number of previous myocardial infarctions, inducibility during programmed stimulation and total mortality during follow-up. In group I, only 1 patient (6%) developed ST depression during exercise compared with 47 patients (35%) in group II (p less than 0.01). After a 34-month mean follow-up, 6 patients in group I (35%) and 18 patients in group II (13%) died suddenly (p = 0.02). It is concluded that sustained monomorphic VT is reproduced during exercise in only 11% of patients with spontaneous late sustained monomorphic VT or VF. Electrocardiographic findings do not support ischemia as a triggering mechanism of exercise-induced sustained monomorphic VT. Patients with exercise-induced sustained monomorphic VT have a high incidence of sudden death.

Ventricular arrhythmias in aortic valve disease: a further marker of impaired left ventricular function

One hundred and twenty stable patients with pure and severe aortic valve disease and without coronary lesions (aortic stenosis, 43 patients; aortic regurgitation, 45 patients; combined aortic stenosis and regurgitation, 32 patients) who had been submitted to haemodynamic studies were prospectively studied with standard electrocardiograms, M-mode echocardiograms, and 24-hour ambulatory electrocardiography (Holter recording). The frequency and complexity of ventricular arrhythmias were related to clinical parameters such as functional class, type of lesion and presence of syncope, and to parameters of left ventricular hypertrophy and function. Ventricular arrhythmias were present in 92% of patients. A high number of ventricular premature beats was directly correlated with parameters of complexity of the arrhythmia. A significant relation was found between electrocardiographic left ventricular hypertrophy and Ryan class (P less than 0.05), and an inverse relation between maximal number of ventricular premature beats in any hour and left ventricular ejection fraction (P less than 0.05). The group of patients with aortic regurgitation showed a higher total number of ventricular premature beats per 24 hours (P less than 0.001), a higher maximal number of these in any hour (P less than 0.01), a higher number of patients with pairs (P less than 0.001), and a higher number of patients in Ryan classes 3, 4A, 4B (P less than 0.01). This study shows a high incidence of ventricular arrhythmias in aortic valve disease, and especially in aortic regurgitation, with a significant relation between left ventricular hypertrophy and function, and number and complexity of arrhythmias.

Effectiveness of oral sotalol for treatment of pediatric arrhythmias

Sotalol is a beta blocker with class III activity. Few investigators have reported its use in pediatric patients. From August 1985 to May 1990, 66 patients (mean age 8.7 years; range 9 days to 24 years), including 14 infants aged less than 3 months, were treated with oral sotalol alone (n = 46) or in association with digoxin (n = 20). Supraventricular reentrant tachycardia was present in 38 patients (20 with documented preexcitation), atrial flutter in 10 and atrial ectopic tachycardia in 7. Three patients had other types of supraventricular tachycardia. Tachycardia was of ventricular origin in 6 patients and both of supraventricular and ventricular origin in the remaining 2. Mean dose of oral sotalol was 135 mg/m2/day given in 2 doses. Congenital heart disease was present in 28 patients, 14 with previous cardiac surgery, mostly at the atrial level. Prior treatment with 1 or more antiarrhythmic agent had been unsuccessful in 83% of patients. Mean duration of treatment was 13.3 months (range 2 months to 5 years). Overall, treatment was successful in 79% of cases. Highest rate of success was observed in patients with supraventricular reentrant tachycardia with or without preexcitation (89%) and in those with atrial ectopic tachycardia (85.5%). Atrial flutter could be controlled in 60% of cases. Sotalol seemed less effective in ventricular tachycardia with a complete control of the arrhythmia being achieved in only 17%; however, it decreased the number of runs of ventricular tachycardia and the number of ventricular premature complexes in 50% of patients. There were no adverse effects in 89% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous variability of ventricular arrhythmias in patients with chronic heart failure

Spontaneous variability of ventricular arrhythmia in patients with chronic heart failure is not well described. We measured this variability in 23 consecutive patients with chronic heart failure who were prospectively enrolled in the placebo limb of a trial concerned with treatment of heart failure. Patients underwent from one to three periods of ambulatory monitoring separated by 1 to 3 months while they were not receiving antiarrhythmic drug treatment. The variability in frequency of premature ventricular complexes (PVCs) was determined at interrecording intervals of 1, 2, and 3 months. The percentage reductions in total PVCs required to exceed the 95% confidence limits of spontaneous variability at these intervals were 91%, 90%, and 97%, respectively. Corresponding values for repetitive beats (beats in couplets and beats in ventricular tachycardia events) were 98%, 80%, and 97% and for ventricular tachycardia events 98%, 83%, and 98%, respectively. The percentage increases in total PVCs, repetitive beats, and ventricular tachycardia events required to identify aggravation of arrhythmia in this study population were 1301%, 4050%, and 6147%, respectively, at 1-month intervals and 2950%, 2868%, and 5938%, respectively, at 3-month intervals. The percentage reductions required to show a true drug effect at 2- and 3-month intervals were 63% and 84% for patients with an ejection fraction less than 0.22 and 89% and 98% for those with an ejection fraction greater than or equal to 0.22 (p less than 0.05 for both). Ventricular arrhythmia would have been missed in 6 (26%) of the 23 patients if only one screening ambulatory recording was available. Thus marked variability in PVCs occurs in patients with chronic heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of disopyramide and mexiletine used alone or in combination in the treatment of ventricular premature beats

The efficacy of oral disopyramide and mexiletine used alone or in combination was studied in 75 patients with frequent ventricular premature beats (VPBs). The efficacy was evaluated with 24-hour ambulatory ECG and greater than or equal to 75% reduction in the number of VPBs was defined as effective. When disopyramide or mexiletine were ineffective or not tolerated, the alternative drug was administered and the efficacy was again evaluated. If the single administration of neither drug was effective, the combination of disopyramide and mexiletine was then given. Either disopyramide or mexiletine was effective in 48 patients, and neither drug was effective in 19 patients. In 19 patients unresponsive to both drugs, combination therapy was effective in six patients (32%). Both drugs caused side effects or one drug caused side effects and another drug was ineffective in eight patients. In five out of those patients, we attempted combined therapy with a reduced dosage of those drugs that caused side effects. This therapy was effective in two patients without intolerable side effects. Thus, when the single use of neither disopyramide nor mexiletine single-drug therapy is effective, it is worthwhile to try combination therapy. Also, combination therapy with a reduced dosage of the drugs that caused side effects might be the therapy of choice in patients who have developed dose-dependent side effects.

Evaluation of antiarrhythmic drug effects with simultaneous analysis of single ventricular premature contractions, couplets and salvos

To improve the clinical value of ambulatory Holter electrocardiographic (ECG) monitoring as a tool of antiarrhythmic therapy control, a new statistical model was developed. In a patient group at increased risk of sudden cardiac death, the spontaneous variability of ventricular arrhythmias was assessed, with simultaneous consideration of single ventricular premature complexes, couplets and salvos. The study included 100 patients who suffered from coronary heart disease or idiopathic dilated cardiomyopathy and for whom greater than 30 ventricular premature complexes/h and couplets had been demonstrated on the last Holter ECG before the study. Between 3 and 12 Holter recordings were made for each patient in a drug-free state; the mean follow-up period was 260 days (maximum 1,403). The mean hourly values of the ectopic events (EE) were assessed separately for ventricular premature complexes, couplets and salvos. The spontaneous variability (SV) was calculated for single ventricular premature complexes, couplets and salvos as SV = log (EEday 2 + 0.01/EEday 1 + 0.01) and linked in one, two and three dimensions. Compared with the consideration of only one type of arrhythmia (one-dimensional model), the simultaneous use of two or three types of arrhythmia (two- or three-dimensional model) resulted in considerably lower reduction and aggravation rates as sufficient proof of drug effects. With control intervals up to 1 week, the one-dimensional model yielded reduction rates for ventricular premature complexes, couplets and salvos of -63%, -90% and -95%, respectively. In contrast, with the three-dimensional model, the rates were -28%, -72% and -88%. The corresponding aggravation values were +370, +1,114% and +2,189% versus +38%, +256% and +747%.(ABSTRACT TRUNCATED AT 250 WORDS)

The haemodynamic effects of bronchoscopy. Comparison of propofol and thiopentone with and without alfentanil pretreatment

The haemodynamic response to bronchoscopy under general anaesthesia was investigated. Forty patients were allocated at random to receive either thiopentone or propofol; half the patients in each group received in addition 18 micrograms/kg of alfentanil one minute before induction of anaesthesia. The heart rate, noninvasive blood pressure and Holter ECG was monitored in all patients. Significant increases in heart rate (p less than 0.05), systolic and diastolic arterial pressures (p less than 0.01) occurred in the thiopentone only group, following bronchoscopy. Systolic and diastolic arterial pressure decreased in patients receiving thiopentone plus alfentanil, following induction of anaesthesia and laryngoscopy (p less than 0.05). No significant haemodynamic changes were seen in either of the groups which received propofol. ST segment changes on subsequent Holter analysis were seen in four patients, but there were no significant differences between the groups. Anaesthesia with propofol alone provides adequate haemodynamic stability for bronchoscopy and the addition is superfluous.

Avoiding interpretive pitfalls when assessing arrhythmia suppression after myocardial infarction: insights from the long-term observations of the placebo-treated patients in the Cardiac Arrhythmia Pilot Study (CAPS)

The Cardiac Arrhythmia Pilot Study (CAPS) was a 1 year trial that analyzed the safety and effectiveness of arrhythmia suppression in 502 patients surviving acute myocardial infarction who had greater than or equal to 10 ventricular premature depolarizations/h or greater than or equal to 5 runs of ventricular tachycardia on a Holter recording obtained 6 to 60 days after the acute infarction. Because 100 of these patients received placebo in a double-blind fashion for 1 year, a comprehensive objective analysis was performed of spontaneous arrhythmia changes based on real data rather than statistical estimates. In the CAPS placebo group, 19% developed some serious clinical event in 1 year (death, heart failure, proarrhythmia) that could likely be attributable to antiarrhythmic drug toxicity. A significant reduction in the frequency of ventricular premature depolarizations (p = 0.004) occurred in the first few weeks of "therapy" with a further significant (p less than 0.04) decrease between 3 to 12 months. After initiation of placebo antiarrhythmic therapy, 27% had "apparent ventricular premature depolarization suppression" (greater than or equal to 70% reduction) after one Holter recording evaluation and nearly half (48%) after six Holter recordings to assess suppression were performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproducibility in circadian rhythm of ventricular premature complexes

To evaluate the existence and reproducibility of a circadian rhythm of ventricular premature complexes (VPCs), 38 patients (mean age 57 +/- 17 years) with greater than or equal to VPCs/hour were studied with 24-hour electrocardiogram Holter monitoring. Nineteen patients had coronary artery disease and 19 had structurally normal hearts. A second Holter electrocardiogram was recorded in all patients from 2 to 47 days (mean 11) after the first. Chronobiologic analysis was made by single and mean cosinor methods. A significant and similar circadian rhythm of VPCs was found in the total sample both on the first (mesor 399, acrophase at 15:08, p less than 0.01) and the second day (mesor 306, acrophase at 14:47, p less than 0.05), with 2 main peaks, the first in the late morning and the second in the afternoon. However, only 18 patients (47%, group A) had a significant individual circadian rhythm of VPCs on both days, whereas 20 (53%, group B) did not have a significant rhythm in greater than or equal to 1 day. A high reproducibility of the circadian rhythm of VPCs was found in group A patients, with a difference of 2.1 +/- 1.8 hours between the acrophases of the 2 days, whereas the difference was 4.4 +/- 3.3 hours in group B patients (p less than 0.01). Among group A patients, 14 (78%) had a VPC rhythm with acrophase occurring during waking hours, whereas the acrophase of 4 (22%) occurred during the night. The reproducibility of the circadian rhythm of VPCs was not influenced by gender, presence of coronary disease, medical therapy, basal VPC number, or day-to-day variability of VPCs, although group A patients were older than group B patients (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous variability in ventricular ectopic activity during chronic antiarrhythmic therapy

Previous determinations of variability in frequency of ventricular arrhythmias have been based on repeated recordings obtained in the absence of therapy. We evaluate variability during "effective" treatment with antiarrhythmic drugs. Variability in the percent suppression of premature ventricular complexes (PVCs) was determined in 55 patients with chronic arrhythmias who underwent multiple ambulatory electrocardiographic recordings during evaluation of chronic therapy with antiarrhythmic drugs initially determined to be effective, which was defined as 70% or more reduction in total PVC frequency or 90% or more reduction in repetitive forms. During chronic therapy, total PVCs were suppressed by 92%, averaged after a logarithmic transformation step, and repetitive beats were suppressed by 88%. Variability in suppression was substantial. The one-sided 95% confidence intervals required a fall in suppression of total PVCs to 40% or less to exceed limits of spontaneous variability and of repetitive PVCs to 66% or less. Suppression declined at least once during therapy to less than 60% for total PVCs in 24 of 55 patients (44%) and to less than 80% for repetitive PVCs in 13 of 33 patients (39%); nine patients (16%) showed increases in PVC frequency at least once to levels above pretreatment baseline. Seven subgroups were analyzed for their effects on variability and loss of suppression: age, gender, disease etiology, cardiac function, baseline PVC frequency, use of beta-blockers, and class of antiarrhythmic drug. Differences in confidence bounds and loss of suppression were found to be determined in a complex way by subgroup differences in variability and in initial levels of PVC suppression. Variability was greater for patient subgroups with greater PVC frequency, beta-blocker therapy, and non-coronary artery disease. However, clinical loss of suppression was more common only in more elderly patients and those with worse cardiac function. In summary, substantial variability in arrhythmia frequency occurs during effective antiarrhythmic therapy, and the 95% confidence limits of spontaneous variability are broad and determined in a complex way. Careful consideration should be given before concluding on the basis of a single Holter test that changes (increases) in arrhythmia frequency, especially in certain subgroups, are caused by treatment failure.

Antiarrhythmic and hemodynamic evaluation of indecainide and procainamide in nonsustained ventricular tachycardia

The present trial was a placebo-controlled, randomized, parallel study comparing indecainide to procainamide. A 24-hour intravenous phase measured and compared invasive hemodynamics, followed by oral administration for assessment of arrhythmia suppression. Thirty-two patients (mean age 61 years) with asymptomatic or mildly symptomatic nonsustained ventricular tachycardia (VT) were evaluated, 15 while receiving indecainide and 17 while receiving procainamide. A total of 8 patients had serious toxicity during the intravenous phase; 6 receiving indecainide experienced increased left ventricular dysfunction or worsening arrhythmia (sustained VT, arrhythmic death) while 2 receiving procainamide developed serious hypotension. Proarrhythmia developed in 3 of 15 (20%) of the indecainide patients, but in no procainamide patient. In those tolerating indecainide, long-term suppression of ventricular premature complexes (VPCs) and of runs of VT was more consistent than with procainamide. While indecainide was a potent suppressor of spontaneous VPCs and VT, patients with significant left ventricular dysfunction could not tolerate it. The indecainide patients developing serious toxicity had a common hemodynamic profile: ejection fraction less than 25%, elevated left ventricular filling pressures, low cardiac and stroke volume index and minimal cardiac reserve. Indecainide has a poor risk-benefit ratio in patients similar to the current population, who have potentially lethal ventricular arrhythmias and severe left ventricular dysfunction.

Low dose quinidine-mexiletine combination therapy versus quinidine monotherapy for treatment of ventricular arrhythmias

Low dose quinidine-mexiletine combination therapy was compared with quinidine monotherapy in 15 patients with frequent ventricular premature complexes and nonsustained ventricular tachycardia in a dose escalation cross-over study. Oral combination therapy was initiated with quinidine gluconate (165 mg) plus mexiletine (150 mg) every 8 h. If ventricular premature complexes were not suppressed greater than or equal to 80% and nonsustained ventricular tachycardia greater than or equal to 90%, the dose was increased to a maximum of 330 mg of quinidine plus 200 mg of mexiletine. Quinidine monotherapy was initiated with 330 mg and escalated to a maximum of 660 mg every 8 h if criteria for effectiveness were not met. Combination quinidine-mexiletine therapy suppressed 80% of ventricular premature complexes in 13 of 14 patients and suppressed 100% of episodes of ventricular tachycardia in 6 of 8 patients (mean quinidine dose 200 +/- 70 mg; mean mexiletine dose 146 +/- 24 mg every 8 h). The mean effective trough quinidine and mexiletine concentration was 1.0 +/- 0.7 and 0.9 +/- 0.4 microgram/ml, respectively. Monotherapy was less effective; that is, greater than or equal to 80% suppression of ventricular premature complexes was observed in 5 of 15 patients and 100% suppression of ventricular tachycardia in 2 of 9 patients. The mean quinidine monotherapy dose was 462 +/- 155 mg every 8 h; the mean quinidine concentration was 1.8 +/- 0.8 microgram/ml. Adverse systemic effects occurred in 3 patients on quinidine-mexiletine therapy and in 11 on quinidine monotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of oral mexiletine therapy at a 12-h dosage interval

The antiarrhythmic effectiveness and safety of 12-h oral administration of mexiletine were evaluated in adult outpatients with a baseline hourly rate of PVCs of 30 or higher who had initially shown at least a 50 percent reduction of this rate when treated with mexiletine at an 8-h dosage interval. Doses were titrated on the basis of 24-h Holter monitoring for both 8- and 12-h intervals. Seventeen of 26 patients showed PVC reductions after 8-h treatment. Fifteen of these 17 patients reached the goal reduction of greater than or equal to 50 percent in the hourly PCV rate with 12-h dosing. Hour-by-hour analysis disclosed a consistent degree of PVC suppression throughout both 8- and 12-h dose intervals. No increase in the incidence of adverse effects was associated with conversion to the 12-h regimen.

Assessing antiarrhythmic drug efficacy: multivariate considerations

The spontaneous variability of ventricular arrhythmias is the major problem in assessing antiarrhythmic drug efficacy. Efficacy is usually assessed on one form of ventricular premature beats, namely either single beats (VPC) or more complex forms like couplets or salvos. The reduction rates required to assume efficacy with a confidence of 95 per cent are 63 per cent for VPCs, 92 per cent for couples or 96 per cent for salvos. These rates are valid for two Holter electrocardiogram recordings within one week; otherwise the rates are higher and close to 100 per cent. In this paper we extend our ratio method for calculating these criteria to consider two or all three forms of ventricular premature beats simultaneously. The method is based on the first principal component. For use in practice we decided to calculate fixed criteria for each form of ventricular premature beats. For the combination of VPCs and couplets and a confidence level of 95 per cent, reduction rates of 42 per cent for VPC and 87 per cent for couplets are required. Both criteria must be fulfilled to assume the efficacy of a drug. These criteria are lower than those for each form alone. For all three forms together, reduction rates of 28, 72 and 88 per cent for VPC, couplets and salvos respectively are required.

The inverse relationship between baseline left ventricular ejection fraction and outcome of antiarrhythmic therapy: a dangerous imbalance in the risk-benefit ratio

Each year, millions of prescriptions are written for antiarrhythmic drug suppression of ventricular arrhythmias. A large portion of these prescriptions are written for patients with asymptomatic, complex ventricular arrhythmias and organic heart disease, termed "potentially malignant" or "potentially lethal." Since arrhythmia suppression in this population is of unproven benefit, we performed the following study: A total of 246 patients (42% with significant left ventricular dysfunction) had complex ventricular arrhythmias, and were treated with one of eight antiarrhythmic drugs (Vaughan Williams classes IA, IB, IC, II, and III). The extent of arrhythmia suppression and the development of serious complications resulting from therapy after 2 weeks was of primary interest. A total of 82 of 246 (33%) maintained adequate (protocol definition) suppression of both ventricular premature beats (VPBs) as well as nonsustained ventricular tachycardia (VT) for 2 weeks, mostly in patients with left ventricular ejection fraction (LVEF) greater than or equal to 40% (p = 0.04 versus LVEF less than 40%). Life-threatening complications of antiarrhythmic therapy occurred most frequently in the 61 patients with an LVEF less than 30% compared to the 185 patients with LVEF greater than or equal to 30% (15% versus 2.1%, p = 0.0005). Suppression of VT was achieved nearly twice as commonly in patients with an LVEF greater than or equal to 30% than in those with an LVEF less than 30% (67% versus 36%; p = 0.0008). Life-threatening complications occurred seven times as frequently in patients presenting with nonsustained VT and an LVEF less than 30% (18% versus 2.3%; p = 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)

Sudden cardiac death: etiologies, pathogenesis, and management

Sudden death claims an estimated 350,000 lives per year in the United States. When death occurs within 1 hour of the onset of symptoms, 90% are the result of ventricular tachyarrhythmias. The majority of victims are middle-aged men with coronary artery disease, but in approximately 25%, sudden death is the presenting manifestation of their problem. In some populations, the detection of premature ventricular complexes (PVCs) by ambulatory monitoring is predictive of an increased risk of sudden death. However, the arrhythmia that best predicts this risk is unclear, and ambient arrhythmias are only a modest marker of this risk. Therapy to suppress asymptomatic PVCs has not been shown to be effective in preventing sudden death, and in some cases, lethal arrhythmias can be prevented without significant effects on ambient arrhythmias. Other risk markers such as depressed left ventricular function and the presence of low-amplitude, long-duration, late potentials recorded on a signal averaged electrocardiogram are more powerful predictors of risk than are PVCs. These latter findings in particular support the presence of areas of slow electrical conduction (a requirement for reentrant mechanism arrhythmias) and suggest that an abnormal electrical environment or "substrate" is the most important factor in this problem. The management of patients at risk for sudden death is controversial. While postinfarct survivors with arrhythmias constitute a population at increased risk, the absolute risk is only about 5% in the first year and has not been shown to be improved by conventional antiarrhythmic drugs. Small study size, arrhythmia variability, ill-defined end points, and proarrhythmia may partially explain this apparent lack of efficacy. The prophylactic use of antiarrhythmic drugs other than beta-blockers to prevent sudden death in asymptomatic populations at risk is therefore of unproven benefit. By contrast, patients who have survived a life-threatening arrhythmia unrelated to an acute myocardial infarction have an approximately 30% risk of recurrence in the following year. In these patients, the use of ambulatory monitoring to guide therapy is limited by the high incidence of false-negative responses (lethal arrhythmia recurrence despite ambient arrhythmia suppression) and the lack of frequent spontaneous arrhythmias in many patients. In this patient population, electrophysiological testing can be used to prognosticate recurrence and gain insight into arrhythmia mechanism, stability, and hemodynamic tolerance. The technique is also useful in guiding both pharmacological and nonpharmacological therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Prevalence and characteristics of proarrhythmia from moricizine (Ethmozine)

Moricizine was studied in 908 patients with ventricular arrhythmia. Proarrhythmia occurred in 29 (3.2%). When the type of proarrhythmia and the type of ventricular arrhythmia were correlated, no proarrhythmic events occurred in patients with benign ventricular arrhythmia. Three of the 4 deaths due to proarrhythmia occurred in patients with lethal ventricular arrhythmia and 14 of the 15 serious proarrhythmic events occurred in patients with potentially lethal ventricular arrhythmia. The overall proarrhythmia incidence in lethal and potentially lethal ventricular arrhythmias was not different (3.2 vs 3.7%, respectively). Proarrhythmia occurred in patients with more significant structural heart disease or conduction defects at baseline, but was not related to the baseline frequency of ventricular premature complexes. There was no relation between dose of moricizine and incidence of proarrhythmia. All 29 proarrhythmic events occurred within 10 days and 26 of 29 (90%) took place within 7 days of therapy start. Thus, moricizine has a low proarrhythmic potential, especially in patients with lethal ventricular arrhythmias, and may have the best risk/benefit ratio among first-line drugs used in these patients.

Values and limitations of programmed stimulation and ambulatory monitoring in the management of ventricular tachycardia

Programmed stimulation (PES) and ambulatory electrocardiographic (Holter) monitoring are both widely used to evaluate the efficacy of antiarrhythmic drugs in patients with recurrent ventricular tachycardia (VT). PES is sensitive but nonspecific, and Holter is specific but insensitive. A failure to suppress ventricular premature complexes (VPCs) on Holter during drug therapy predicts a poor outcome. A suppression of VPCs by drug therapy, however, does not preclude a poor outcome. If VT is no longer induced by PES during drug therapy, the patients will have a good outcome. A persistent induction of VT during drug therapy, however, does not preclude good outcomes. Therefore some investigators have suggested alternative PES efficacy criteria such as the changes in the rate of induced VT during therapy. Further studies should be conducted to confirm this. Because both methods have values and limitations, a combined use of the 2 methods is recommended to improve the clinician's ability to predict the outcome of antiarrhythmic therapy. Studies designed to prove that 1 method is better than the other may prove futile.

Role of invasive electrophysiologic testing in the management of life-threatening ventricular arrhythmias

Electrophysiologic studies are indicated in patients with sustained paroxysmal ventricular tachycardia, ventricular fibrillation or aborted sudden death. These studies allow determination of mechanism and reproducibility of initiation as well as pacing termination of ventricular tachycardia, against which the effects of pharmacologic or nonpharmacologic therapies can be tested. Such studies are also indicated in certain patients with syncope in whom a strong suspicion exists for an arrhythmic cause. The content and conduct of electrophysiologic testing in these patients require attention to the physiology of the conduction system and systematic programmed stimulation of the right ventricle. The stimulation protocol should include, if necessary, twice-threshold stimulation at 2 sites at 3 or more cycle lengths, with up to 3 extrastimuli. Sufficient variability exists in electrophysiologic testing as in other clinical methods calling for careful attention to the reproducibility of tachycardia induction in a given patient, lest chance alone mimic beneficial or deleterious effects of antiarrhythmic regimens. Mapping-directed surgery for ventricular tachycardia remains the most effective therapy in patients with sustained monomorphic ventricular tachycardia with a mortality similar to other forms of medical therapy.

The natural history of benign and potentially malignant ventricular arrhythmias with special reference to nonsustained ventricular tachycardia

Ambulatory ECG recordings are routinely used to identify patients at increased risk of sudden cardiac death and to monitor changes in ventricular arrhythmias during antiarrhythmic drug therapy. The arrhythmia frequency established during the initial baseline has previously been reported to change during a second placebo monitoring period in patients with non-life-threatening ventricular arrhythmias, but the extent to which this applies to patients with nonsustained ventricular tachycardia has not been examined. To extend these observations to patients with potentially lethal ventricular arrhythmias, we studied 53 patients enrolled in one of two investigational antiarrhythmic drug trials that introduced a second single-blind placebo period (placebo-pulse) an average of 16 months after successful arrhythmia suppression. Thirty-eight of the 53 patients had runs of nonsustained ventricular tachycardia recorded during the initial baseline (placebo I) period, with 63% averaging greater than or equal to 10 runs per day. There was a marked reduction in the arrhythmia frequencies between the two placebo periods: 55% for ventricular premature beats, and 77% for pairs (p less than 0.001, respectively). Of the 38 patients with nonsustained ventricular tachycardia, there was a 72% reduction (892 +/- 531 vs 245 +/- 18 runs of VT/day, placebo I vs II; p = 0.0001), with 32% having total suppression of nonsustained ventricular tachycardia during the second placebo period. The results of this trial extend our previous observations of long-term spontaneous changes in arrhythmia frequency to patients with symptomatic, potentially lethal ventricular arrhythmia and support the recommendation for periodic reassessment of baseline arrhythmia frequency to determine the continued need for antiarrhythmic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)