Factors causing arrhythmias in chronic congestive heart failure

Sympathetic crashing acute pulmonary edema following pacemaker insertion

Key Clinical Message

Sympathetic crashing acute pulmonary edema (SCAPE) complicating pacemaker implantation is a very uncommon and dangerous occurrence. Following pacemaker implantation, patients need stringent monitoring, and compelling evidence about SCAPE treatment is required.

Abstract

Sympathetic crashing acute pulmonary edema complicating a pacemaker insertion as the case in our patient is extremely rare. We report a case of 75-year-old man with a complete AV block, which requires urgent pacemaker implantation. Half an hour following the insertion of the pacemaker, an abrupt SCAPE emerged and the patient was incubated immediately.

COVID-19 and arrhythmia: An overview

Arrhythmias in COVID-19 patients are associated with hypoxia, myocardial ischemia, cytokines, inflammation, electrolyte abnormalities, pro-arrhythmic or QT-prolonging medications, and underlying heart conditions such as severe congestive heart failure, inherited arrhythmia syndromes, or congenital heart conditions. In the pediatric population, multisystem inflammatory syndrome can lead to cardiac injury and arrhythmias. In addition, arrhythmias and cardiac arrests are most prevalent in the critically ill intensive care unit COVID-19 patient population. This review presents an overview of the association between COVID-19 and arrhythmias by detailing possible pathophysiological mechanisms, existing knowledge of pro-arrhythmic factors, and results from studies in adult and pediatric COVID-19 populations, and the clinical implications.

Intracellular ATP binding is required to activate the slowly activating K+ channel I(Ks)

Gating of ion channels by ligands is fundamental to cellular function, and ATP serves as both an energy source and a signaling molecule that modulates ion channel and transporter functions. The slowly activating K(+) channel I(Ks) in cardiac myocytes is formed by KCNQ1 and KCNE1 subunits that conduct K(+) to repolarize the action potential. Here we show that intracellular ATP activates heterologously coexpressed KCNQ1 and KCNE1 as well as I(Ks) in cardiac myocytes by directly binding to the C terminus of KCNQ1 to allow the pore to open. The channel is most sensitive to ATP near its physiological concentration, and lowering ATP concentration in cardiac myocytes results in I(Ks) reduction and action potential prolongation. Multiple mutations that suppress I(Ks) by decreasing the ATP sensitivity of the channel are associated with the long QT (interval between the Q and T waves in electrocardiogram) syndrome that predisposes afflicted individuals to cardiac arrhythmia and sudden death. A cluster of basic and aromatic residues that may form a unique ATP binding site are identified; ATP activation of the wild-type channel and the effects of the mutations on ATP sensitivity are consistent with an allosteric mechanism. These results demonstrate the activation of an ion channel by intracellular ATP binding, and ATP-dependent gating allows I(Ks) to couple myocyte energy state to its electrophysiology in physiologic and pathologic conditions.

Cardiac troponin I and ventricular arrhythmia in patients with chronic heart failure

BACKGROUND

Both detectable serum cardiac troponin I (cTnI) and ventricular dysrhythmias are common in patients with chronic heart failure (CHF) and are paralleled with the severity of the CHF. However, the relationship between serum cTnI and ventricular arrhythmia severity in patients with CHF remains unknown; the mechanism of the ventricular arrhythmia in the CHF patients also remains unclear.

MATERIALS AND METHODS

The study group included 218 patients with CHF who had cTnI assay drawn at the time of initial presentation. Patients with acute myocardial infarction or myocarditis were excluded from the analysis. The patients were divided into two groups: cTnI-positive with serum cTnI > 0.5 ng mL(-1) (n = 98) and cTnI-negative with serum cTnI < or = 0.5 ng mL(-1) (n = 120). The severity of ventricular dysrhythmias was assessed by 24-h Holter monitoring, using prospectively defined measures of ventricular arrhythmic burden.

RESULTS

Prevalence of risk factors for ventricular dysrhythmias was equal in both groups. All measures of ventricular ectopy were much higher in patients of the cTnI-positive groups. Mean hourly ventricular pairs (13.59 +/- 10.3 vs. 11.1 +/- 6.01, P = 0.027), mean hourly repetitive ventricular beats (26.01 +/- 13.67 vs. 22.01 +/- 13.56, P = 0.032), and the frequency of ventricular tachycardia episodes per 24 h (12.54 +/- 16.68 vs. 7.68 +/- 11.54, P = 0.012) were higher in patients with detectable cTnI levels. After inclusion of clinical variables and drug therapies in a multivariate analysis, the positive relationship between cTnI and the frequency of ventricular pairs (P = 0.03), repetitive ventricular beats (P = 0.037), and ventricular tachycardia (P = 0.03) remained independent. In multivariate logistic regression, the risk of developing ventricular tachycardia was higher in patients with detectable cTnI levels with an adjusted odds ratio (OR) of 2.31 (95% CI, 1.22-2.65, P = 0.003).

CONCLUSIONS

In patients with CHF, serum cTnI is closely related to increased occurrence of ventricular dysrhythmias and could identify a subgroup of patients with ventricular tachycardia. The minimal myocardial injury detected by serum cTnI might be the abnormal substrate for ventricular dysrhythmias.

Ryanodine receptor-targeted anti-arrhythmic therapy

Cardiac arrhythmia is an important cause of death in patients with heart failure (HF) and inherited arrhythmia syndromes, such as catecholaminergic polymorphic ventricular tachycardia (CPVT). Alterations in intracellular calcium handling play a prominent role in the generation of arrhythmias in the failing heart. Diastolic calcium leak from the sarcoplasmic reticulum (SR) via cardiac ryanodine receptors (RyR2) may initiate delayed afterdepolarizations and triggered activity leading to arrhythmias. Similarly, SR Ca(2+) leak through mutant RyR2 channels may cause triggered activity during exercise in patients with CPVT. Novel therapeutic approaches, based on recent advances in the understanding of the cellular mechanisms underlying arrhythmias in HF and CPVT, are currently being evaluated to specifically correct defective Ca(2+) release in these lethal syndromes.

A pilot safety trial of prolonged (48 h) infusion of the dual endothelin-receptor antagonist tezosentan in patients with advanced heart failure

STUDY OBJECTIVES

Tezosentan, an IV dual endothelin-receptor antagonist, has demonstrated beneficial hemodynamic effects in patients with advanced heart failure. In addition, no notable differences in safety and tolerability variables were detected between tezosentan-treated and placebo-treated patients when infused over 4 to 6 h. The present study was conducted primarily to assess the safety and tolerability of tezosentan when administered over a prolonged, 48-h treatment period, and secondarily to investigate hemodynamic response.

DESIGN

This randomized, double-blind, active-controlled study of continual IV administration of two dosages of tezosentan (20 mg/h and 50 mg/h; n = 6 each) or dobutamine (5 microg/kg/min; n = 2) over 48 h in patients with advanced heart failure was conducted to assess tolerability, safety, and hemodynamic variables (Doppler echocardiography).

RESULTS

During tezosentan infusion, no episodes of hypotension requiring withdrawal of therapy occurred, and hemodynamic rebound was not observed after abrupt cessation of the infusion. There were no reports of worsening heart failure in tezosentan-treated patients up to 28 days following the infusion. The most common side effect during the infusion was headache (9 of 12 tezosentan-treated patients and both dobutamine-treated patients). Echocardiographic Doppler measurements suggested improvements in cardiac index, pulmonary capillary wedge pressure, and relaxation properties as well as in diastolic and systolic function in all treatment groups.

CONCLUSIONS

Prolonged, 48-h IV dual endothelin-receptor antagonism with tezosentan was well tolerated with no new safety concerns emerging. These data further support the potential role of tezosentan in the treatment of patients with acute heart failure.

Hemodynamic effects of tezosentan, an intravenous dual endothelin receptor antagonist, in patients with class III to IV congestive heart failure

BACKGROUND

Endothelin-1, a powerful mediator of vasoconstriction, is increased in patients with congestive heart failure and appears to be a prognostic marker that strongly is correlated with the severity of disease. However, little is known about the potential immediate beneficial effects of acute blockade of the endothelin system in patients with symptomatic left ventricular dysfunction. We assessed the hemodynamic effects and safety of tezosentan, an intravenous dual endothelin receptor antagonist, in patients with moderate to severe heart failure.

METHODS AND RESULTS

This randomized placebo-controlled study evaluated the hemodynamic effects of 6-hour infusions of tezosentan at 5, 20, 50, and 100 mg/h compared with placebo in 61 patients with New York Heart Association class III to IV heart failure. Plasma endothelin-1 and tezosentan concentrations were also determined. Treatment with tezosentan caused a dose-dependent increase in cardiac index ranging from 24.4% to 49.9% versus 3.0% with placebo. Tezosentan also dose-dependently reduced pulmonary capillary wedge pressure and pulmonary and systemic vascular resistances, with no change in heart rate. No episodes of ventricular tachycardia or hypotension requiring drug termination were observed during tezosentan infusion. Tezosentan administration resulted in dose-related increased plasma endothelin-1 concentrations.

CONCLUSIONS

The present study demonstrated that tezosentan can be safely administered to patients with moderate to severe heart failure and that by virtue of its ability to antagonize the effects of endothelin-1, it induced vasodilatory responses leading to a significant improvement in cardiac index. Further studies are under way to determine the clinical effects of tezosentan in the setting of acute heart failure.

An animal model of arrhythmogenesis in congestive heart failure

Background: Patients with congestive heart failure (CHF) frequently die from arrhythmias, but models to study arrhythmogenic mechanisms during progressive CHF are lacking. Consequently we examined the feasibility of using dogs with an ischemic insult followed by rapid pacing to study ventricular arrhythmias in CHF. Methods: Eighteen chronically instrumented dogs had ischemic damage induced by inflating a balloon tipped catheter in a coronary artery for 90 min. After 2 weeks recovery, electrophysiologic studies were performed on no drugs, during esmolol infusion, and during isoproterenol infusion. The pacer was turned on at 250 bpm in 12 dogs, but not in six controls, and studies repeated bi-weekly for up to 6 weeks. Results: Serial echocardiograms documented progressive CHF, and serial signal averaged electrocardiograms demonstrated prolongation of total QRS, increased duration of terminal QRS<40 mv, and decreased RMS voltage of the terminal 20 ms of QRS in paced dogs. Arrhythmia severity increased as CHF progressed, but responses were quite variable, unaffected by esmolol, and minimally altered by isoproterenol. Conclusions: Ischemic left ventricular damage followed by rapid ventricular pacing in dogs produces a model that closely mimics patients with CHF and ventricular arrhythmias, including a heterogeneous pathophysiologic response to intervention.

Familial dilated cardiomyopathy and spontaneous ventricular arrhythmias

Two members of a family with (autosomal dominant) dilated cardiomyopathy and symptomatic short-lasting ventricular tachyarrhythmias were each treated with an ICD in the course of their disease. One patient had an episode of torsades de pointes induced by amiodarone, and the ICD failed to recognize some events. Cardiac arrest recurred in this setting. Treatment with bisoprolol was helpful in maintaining an acceptable functional status and in preventing multiple shocks until transplantation became mandatory. Bisoprolol was not tolerated by the second patient, who had several episodes of syncope because of nonsustained ventricular tachycardia. His functional course went downhill fast, and he received a heart transplantation 16 months after implantation of an ICD, which had not delivered any shocks, in spite of one symptomatic short ventricular tachycardia.

Pronounced increase in defibrillation threshold associated with pacing-induced cardiomyopathy in the dog

Progressive changes in myopathology after implantation of an automatic defibrillator could compromise device efficacy. The influence of heart failure development on the defibrillation threshold was evaluated by means of a rapid ventricular pacing model of heart failure in dogs. After transvenous pacemaker lead implantation, adult mongrel dogs were randomly assigned to either the control (n = 7) or rapidly paced group (240 beats/min, n = 6). Seventeen days after implantation, triplicate determinations of the defibrillation threshold were made with three epicardial electrodes. The average defibrillation threshold was four times higher in the rapidly paced group, 13.3 +/- 2.0 joules (mean +/- SEM), than in the control group, 3.3 +/- 0.7 joules (p < 0.01), and was significantly correlated with ventricular weight (r = 0.70, p < 0.01). Both defibrillation threshold energy per gram of ventricle and ventricular weight corrected for body weight were significantly higher in rapidly paced dogs compared with control dogs. It was concluded that myocardial hypertrophy and heart failure may profoundly increase defibrillation energy requirements.

First- or second-degree atrioventricular block as a risk factor in idiopathic dilated cardiomyopathy

To evaluate the significance of clinical, hemodynamic and electrocardiographic risk factors in idiopathic dilated cardiomyopathy 94 patients were followed prospectively for 49 +/- 37 months. During follow-up, 30 patients died, 13 died suddenly, 13 died of congestive heart failure and 4 of other causes. Follow-up was completed in 85 patients, and overall cardiac mortality was 31%. Univariate analysis revealed left ventricular ejection fraction among 20 variables as the major indicator of risk of both cardiac death of all causes and sudden cardiac death separately. Multivariate overall analysis determined 3 independent risk factors in the following order for all causes of cardiac death: Ventricular pairs > 40/24 hours (RR 7.2, p < 0.0001), left ventricular ejection fraction < or = 35% (RR 6.5, p < 0.001) and first- or second-degree atrioventricular (AV) block (RR 3.1, p < 0.05). In the subset of patients with ejection fraction < or = 35% ventricular pairs > 40 per 24 hours (RR 10.7, p < 0.001), AV block (RR 3.9, p < 0.05), and the missing administration of vasodilators (RR 3.3, p < 0.05) were the most important. The chief risk factors for sudden cardiac death were age (RR 7.4, p < 0.01) and AV block (RR 4.6, p < 0.05) by adjustment for age, and ejection fraction < or = 35% (RR 7.1, p < 0.01) and AV block (RR 4.2, p < 0.05) if not adjusted for age. A differentiation into 4 risk groups was attempted. The additional independent prognostic importance of AV block was shown, especially in combination with reduced ejection fraction or a high incidence of ventricular pairs.(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)

Diagnostic value of ventricular stimulation in patients with idiopathic dilated cardiomyopathy

To assess the response to programmed ventricular stimulation and the clinical outcome, we performed a prospective study in 103 patients with idiopathic dilated cardiomyopathy. The protocol used up to three extrastimuli delivered at two right ventricular sites during sinus rhythm and ventricular pacing at 100 and 150 beats/min and was repeated during infusion of 1 to 4 micrograms/min of isoproterenol. Sustained monomorphic ventricular tachycardia (VT) was induced in 8 of 11 patients with spontaneous sustained VT, in none of 35 patients without significant ventricular arrhythmias during Holter monitoring, and in 9 of 56 patients with salvos of ventricular premature beats. Isoproterenol infusion facilitated the induction of two episodes of sustained VT in patients with spontaneous sustained VT; however, in all but one of the remaining patients, induction of ventricular tachyarrhythmias was not impaired. During the follow-up period there were eight sudden deaths among patients who initially had syncope, inducible sustained VT, or both and three episodes of sustained VT in patients who initially had nonsustained VT but inducible sustained VT. Isoproterenol infusion can be used to safely facilitate induction of ventricular tachyarrhythmias in patients with dilated cardiomyopathy. The induction of sustained VT was associated with a poor prognosis.

"Silent" heart failure as observed by a French cardiologist

As the precursor of overt heart failure, with its grim prognosis, "silent" heart failure is a concept that bears examination. The pathophysiology of congestive heart failure and the mechanisms of the impact of hypertension on the development of left ventricular hypertrophy, and silent and overt heart failure are investigated. In addition, the reasons why diuretics, especially potassium-sparing diuretics such as spironolactone, remain the most effective treatment of mild congestive heart failure, and their role in preventing the evolution of silent to overt heart failure are explained.

Effect of acute hemodynamic decompensation on electrical inducibility of ventricular arrhythmias in patients with dilated cardiomyopathy and complex nonsustained ventricular arrhythmias

In patients with dilated cardiomyopathy, hemodynamic decompensation has been postulated to increase vulnerability to reentrant ventricular arrhythmias. To test this hypothesis, we performed programmed ventricular stimulation with three extrastimuli on nine patients with dilated cardiomyopathy and asymptomatic complex ventricular arrhythmias during a period of acute hemodynamic decompensation; programmed ventricular stimulation was then repeated following hemodynamic improvement with nitroprusside. These patients did not have a history of documented or suspected sustained ventricular tachycardia or fibrillation. The mean left ventricular ejection fraction was 0.21 +/- 0.04 (range 0.15 to 0.26). In the baseline state, mean right atrial pressure was 8 +/- 4 mm Hg, pulmonary artery wedge pressure was 20 +/- 3 mm Hg, and cardiac index was 3.2 +/- 0.5 L/min/m2. Following acute hemodynamic decompensation, mean right atrial pressure increased to 16 +/- 5 mm Hg and pulmonary artery wedge pressure to 33 +/- 8 mm Hg; cardiac index decreased to 2.1 +/- 0.5 L/min/m2. In this decompensated state, programmed ventricular stimulation failed to induce sustained or nonsustained ventricular arrhythmias in any patient. Following nitroprusside administration (mean dose 1.5 +/- 1.1 micrograms/kg/min), there were significant decreases in mean right atrial pressure (11 +/- 3 mm Hg) and pulmonary artery wedge pressure (16 +/- 3 mm Hg), and a significant increase in cardiac index (3.1 +/- 1.1 L/min/m2) (p less than 0.05 for all values versus the decompensated state). In the improved hemodynamic state, programmed ventricular stimulation induced nonsustained ventricular tachycardia (six beats) in only one patient, and sustained arrhythmias in none.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiarrhythmic drug therapy for congestive heart failure with focus on moricizine

Many patients who have serious ventricular arrhythmia requiring antiarrhythmic drug therapy have congestive heart failure (CHF). However, the pharmacokinetic and pharmacodynamic properties of the antiarrhythmic drugs are altered in the presence of CHF. It has been reported that some adverse effects, primarily aggravation of arrhythmia and CHF occur more frequently in patients with a history of left ventricular (LV) dysfunction. Moreover, antiarrhythmic drugs are less effective in patients with a history of CHF and a reduced LV ejection fraction (LVEF). Moricizine, a new antiarrhythmic drug, has been undergoing clinical trials for over 13 years in the United States. The data base involving 1,072 patients was analyzed to establish the effect of this agent in patients with CHF. The presence of CHF does not alter the absorption, half-life and clearance of moricizine. The incidence of CHF exacerbation definitely related to moricizine was low (2%) and occurred primarily in patients with a history of CHF. Aggravation of arrhythmia and conduction abnormalities also occurred more often in patients with prior CHF. However, the incidence of all other adverse effects involving other organ systems was the same in patients with and without CHF and was also unrelated to the baseline LVEF. The effect of moricizine for suppressing spontaneously occurring ventricular ectopy was also similar in patients with and without CHF and was independent of LVEF. However, the drug is less effective in preventing sustained ventricular arrhythmia in patients with CHF.

Programmed ventricular stimulation in patients with left ventricular dysfunction and ventricular tachycardia: effects of acute hemodynamic improvement due to nitroprusside

To assess the electrophysiologic effects of acute hemodynamic improvement in patients with left ventricular systolic dysfunction, 12 patients with a left ventricular ejection fraction less than 0.40 and a history of sustained monomorphic ventricular tachycardia were studied. All patients had underlying coronary artery disease. Patients underwent programmed cardiac stimulation in random order during a baseline period and with nitroprusside infusion. Mean pulmonary capillary wedge pressure decreased from 20 +/- 8 mm Hg at baseline study to 8 +/- 3 mm Hg during nitroprusside infusion (p less than 0.0001). Pulmonary artery, right atrial and systemic arterial pressures also decreased with nitroprusside (p less than 0.01). Cardiac output did not change. Left ventricular dimensions, determined by two-dimensional echocardiography, decreased significantly during nitroprusside infusion. The right ventricular effective refractory period, measured during ventricular drive trains at cycle lengths of 400 and 600 ms, were similar during baseline and nitroprusside periods (271 +/- 30 versus 274 +/- 31 ms at 600 ms, and 249 +/- 25 versus 246 +/- 18 ms at 400 ms). In 2 patients no ventricular arrhythmias were induced during either study period; in the other 10, ventricular tachyarrhythmias were induced during both periods. The mean number of extrastimuli required to induce a ventricular tachyarrhythmia was similar during the baseline period (1.8 +/- 0.6) and during nitroprusside infusion (1.9 +/- 0.7). As well, the mean cycle length of ventricular tachycardia induced was similar during the baseline period (347 +/- 61 ms) and during nitroprusside infusion (342 +/- 70 ms).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiology of phosphodiesterase inhibitors

Phosphodiesterase inhibitors appear to uniformly enhance atrioventricular node conduction, although milrinone seems to have the least effect. Except for digoxin, this effect on atrioventricular node conduction is similar to that noted with other inotropic agents. Other electrophysiologic effects vary among patients, with enoximone being more theophylline-like in response. Because none of these drugs do not have an adverse effect on His-Purkinje conduction, they are safe to use in patients with intraventricular conduction disturbances. Significant proarrhythmia is uncommon, but can occur. The mechanisms causing these electrophysiologic changes are not well defined, but the changes may occur because of increased concentrations of cytosol cyclic adenosine monophosphate secondary to phosphodiesterase inhibition, increased cytosol calcium levels secondary to increased cyclic adenosine monophosphate, or reflex adrenergic stimulation secondary to the peripheral vasodilating effects of these drugs.