Changes in plasma concentrations of atrial natriuretic peptides after cardioversion of chronic atrial fibrillation

Reduction over time of QTc prolongation in patients with sotalol after cardioversion of atrial fibrillation

BACKGROUND

Sotalol is recommended to prevent relapse of atrial fibrillation after cardioversion (CV). Sotalol prolongs the action potential by blocking the rapid component of the delayed rectifier potassium current, which results in corrected QT (QTc) prolongation on the electrocardiogram. Pronounced QTc prolongation may lead to proarrhythmias and sudden death.

OBJECTIVE

We investigated the dynamics of the QTc interval during the week after CV in patients treated with sotalol compared with patients treated with a β-blocker.

METHODS

Patients who underwent elective CV for persistent atrial fibrillation and maintained sinus rhythm for 1 week were included prospectively. All patients were on the highest tolerable stable dose of metoprolol or sotalol. Twelve-lead electrocardiograms were recorded 1 hour and 1 week after CV.

RESULTS

A total of 104 patients on sotalol and 104 on metoprolol were included; clinical characteristics between groups were comparable. One hour after CV, the QTc interval was significantly longer in sotalol-treated patients than in metoprolol-treated patients (465 ± 25 ms vs 423 ± 30 ms; P ≤ .0001). After 1 week, the QTc interval was reduced by -20.3 ± 24 ms in sotalol-treated patients (P ≤ .001); no such effect was seen in metoprolol-treated patients (-2.5 ± 18 ms; P = 0.28). The heart rate was stable during the week in both groups. In multivariate analysis of sotalol-treated patients, factors contributing to pronounced reduction in the QTc interval were longer QTc interval after CV and renal function.

CONCLUSION

The QTc interval is significantly reduced during the week after CV to sinus rhythm in sotalol-treated patients. This provides insight into the increased risk of proarrhythmias in the immediate time period after CV.

Genome wide analysis of drug-induced torsades de pointes: lack of common variants with large effect sizes

Marked prolongation of the QT interval on the electrocardiogram associated with the polymorphic ventricular tachycardia Torsades de Pointes is a serious adverse event during treatment with antiarrhythmic drugs and other culprit medications, and is a common cause for drug relabeling and withdrawal. Although clinical risk factors have been identified, the syndrome remains unpredictable in an individual patient. Here we used genome-wide association analysis to search for common predisposing genetic variants. Cases of drug-induced Torsades de Pointes (diTdP), treatment tolerant controls, and general population controls were ascertained across multiple sites using common definitions, and genotyped on the Illumina 610k or 1M-Duo BeadChips. Principal Components Analysis was used to select 216 Northwestern European diTdP cases and 771 ancestry-matched controls, including treatment-tolerant and general population subjects. With these sample sizes, there is 80% power to detect a variant at genome-wide significance with minor allele frequency of 10% and conferring an odds ratio of ≥2.7. Tests of association were carried out for each single nucleotide polymorphism (SNP) by logistic regression adjusting for gender and population structure. No SNP reached genome wide-significance; the variant with the lowest P value was rs2276314, a non-synonymous coding variant in C18orf21 (p  =  3×10⁻⁷, odds ratio = 2, 95% confidence intervals: 1.5–2.6). The haplotype formed by rs2276314 and a second SNP, rs767531, was significantly more frequent in controls than cases (p  =  3×10⁻⁹). Expanding the number of controls and a gene-based analysis did not yield significant associations. This study argues that common genomic variants do not contribute importantly to risk for drug-induced Torsades de Pointes across multiple drugs.

A rate-independent method of assessing QT-RR slope following conversion of atrial fibrillation

INTRODUCTION

Following conversion of atrial fibrillation (AF), QT interval transiently and variably prolongs and can trigger torsades de pointes (TdP). However, quantitative analysis of risk in this setting is difficult because cycle length variability during AF makes rate-corrected QT impossible to calculate. In this study, a newly developed method to study heart rate dependence of the QT interval during AF was applied to assess the QT-RR relationships prior to and following cardioversion in patients with AF.

METHODS AND RESULTS

Cardiac rhythm was digitized for > or = 30 minutes prior to and following elective cardioversion to sinus rhythm (SR) in 12 patients. Each QT interval was placed in a "bin" (50 ms), according to the preceding RR interval. All QT intervals within a bin were averaged and RR bin-specific QT values were derived. The slope of the QT-RR relationship was much flatter in AF (0.058 +/- 0.02) compared with that predicted by conventionally used QT rate corrections (0.130 [Bazett], 0.096 [Fridericia]) and much steeper after cardioversion (0.238 +/- 0.14, P < 0.01 compared with AF). The method also allowed us to establish that QT at any given RR interval prolonged when SR was restored (e.g., at RR interval 800 ms: QT = 0.38 +/- 0.03 second [AF] vs 0.46 +/- 0.05 second [SR], P < 0.01). The longest QT values were in patients receiving sotalol or quinidine.

CONCLUSIONS

The results of this study demonstrate that QT interval can be reliably measured in AF using a method that is independent of heart rate. We also showed that cardioversion of AF acutely increases the QT interval and the steepness of the QT-RR slope.

Acute anticoagulation adjustment in patients with atrial fibrillation at risk for stroke: approaches, strategies, risks and benefits

The acute management of anticoagulation in patients with atrial fibrillation to prevent stroke and other thromboembolic complications includes the use of individualized strategies tailored to the patient and based on the situation (cardioversion, surgeries, dental procedures, cardiac interventions, other invasive procedures and initiation of, or adjustment to, warfarin dosing). The vast range of choices can cause confusion and few randomized controlled clinical trials in this area provide adequate guidance. Chronic anticoagulation management is more straightforward since clinical evidence is ample, randomized clinical trial data provides cogent informaiton and guidelines have been established. Acute management of anticoagulation in patients with atrial fibrillation to prevent thromboembolic complications is often unrecognized but is emerging as a crucial, but challenging, and increasingly complex aspect of the care of patients with atrial fibrillation. This review addresses issues regarding such patients who may be at risk for stroke and require acute adjustments of anticoagulation (in light of, or in lieu of, chronic anticoagulation). Several promising new strategies are considered in light of established medical care. This analysis provides practical recommendations based on available data and presents results from recent investigations that may provide insight into future strategies.

Atrial natriuretic peptide level after cardioversion of chronic atrial fibrillation

Heart endocrine studies concerning patients with chronic atrial fibrillation (AF) have become increasingly important. Atrial natriuretic peptide (ANP) is released from atrial myocytes. The increased level of ANP in patients with AF is probably caused by the hemodynamic effect of the arrhythmia. The aim of this study was to explore plasma ANP levels in patients with chronic AF and to describe plasma ANP concentration changes following sinus rhythm (SR) restoration. The study group was comprised of 42 patients, aged between 43 and 76 years with chronic AF (more than 1 month) and a relatively controlled ventricular response (85.8+/-11.3 beats/min). Plasma ANP levels were measured before and 24 h after AF cardioversion. The control group comprised of 11 subjects. All had normal SR without history of AF and were compatible in age, sex and concomitant diseases with the examined group. ANP level values were expressed as mean+/-standard deviation. The mean plasma ANP level in the AF group was significantly higher than in the control group (59.5+/-15.6 vs. 34.3+/-10.2 pg/ml, P<0,001). Electrical or pharmacological cardioversion was performed in 42 patients. SR was successfully restored in 35 patients. Plasma ANP concentrations decreased significantly from baseline values (from 59.4+/-16.6 to 31.4+/-15.0 pg/ml, P<0.001) 24 h after cardioversion in the successful group, while they remained unchanged (60.2+/-10.7 to 59.4+/-10.4 pg/ml, NS) in patients with an unsuccessful cardioversion.

CONCLUSION

The mean concentration of ANP in patients with chronic AF was nearly two-times higher than in the control group with sinus rhythm. Conversion to SR was associated with a significant decrease and normalization in plasma ANP concentrations.

Plasma cardiac natriuretic peptides as biochemical markers of recurrence of atrial fibrillation in patients with mild congestive heart failure

To determine changes in plasma brain natriuretic peptide (BNP) after direct current cardioversion (DC) and to evaluate the relationship between plasma atrial natriuretic peptide (ANP) and BNP and the recurrence of atrial fibrillation (AF) after DC in patients with mild congestive heart failure (CHF), plasma ANP and BNP were measured before and after DC in 71 patients with mild CHF and then followed. In 65 patients with successful DC, both ANP and BNP decreased 15 min after DC. Cox stepwise multivariate analysis among 14 variables such as age, history of AF, echocardiographic parameters, medication and ANP and BNP revealed that only low ANP (p=0.005) and high BNP before DC (p=0.0002) were independent predictors of recurrent AF. A ratio of ANP to BNP less than 0.44 was a significant risk factor for AF recurrence by Kaplan-Meier analysis (p=0.02). BNP began to decrease immediately after successful DC. High BNP and relatively low ANP compared with BNP were independent risk factors of AF recurrence in patients with mild CHF.

Exaggerated QT prolongation after cardioversion of atrial fibrillation

OBJECTIVES

The purpose of this study was to test the hypothesis that the extent of drug-induced QT prolongation by dofetilide is greater in sinus rhythm (SR) after cardioversion compared with during atrial fibrillation (AF).

BACKGROUND

Anecdotes suggest that when action potential-prolonging antiarrhythmic drugs are used for AF, excessive QT prolongation and torsades de pointes (TdP) often occur shortly after sinus rhythm is restored.

METHODS

QT was measured in nine patients with AF who received two identical infusions of dofetilide: 1) before elective direct current cardioversion and 2) within 24 h of restoration of SR.

RESULTS

During AF, dofetilide did not prolong QT (baseline: 368 +/- 48 ms vs. drug: 391 +/- 60, p = NS) whereas during SR, QT was prolonged from 405 +/- 55 to 470 +/- 67 ms (p < 0.01). In four patients (group I), the SR dofetilide infusion was terminated early because QT prolonged to >500 ms, and one patient developed asymptomatic nonsustained TdP. The remaining five patients (group II) received the entire dose during SR. Although deltaQT was greater in group I during SR (91 +/- 22 vs. 45 +/- 25 ms, p < 0.05), plasma dofetilide concentrations during SR were similar in the two groups (2.72 +/- 0.96 vs. 2.77 +/- 0.25 ng/ml), and in AF (2.76 +/- 1.22 ng/ml). DeltaQT in SR correlated inversely with baseline SR heart rate (r = -0.69, p < 0.05), and QT dispersion developing during the infusion (r = 0.79, p < 0.01).

CONCLUSIONS

Shortly after restoration of SR, there was increased sensitivity to QT prolongation by this I(Kr)-specific blocker. Slower heart rates after cardioversion and QT dispersion during treatment appear to be important predictors of this response.

Atrial reservoir and active transport function after cardioversion of chronic atrial fibrillation

Atrial reservoir function has not been studied after successful cardioversion of chronic atrial fibrillation. Using transthoracic and transesophageal Doppler echocardiography, we measured flow velocity-time integrals of the systolic forward (Sa), diastolic forward (Da), and diastolic reversed (rAa) waves of flow velocity waveforms in the pulmonary vein and the superior vena cava, and those of the early diastolic (Ea) and late diastolic (Aa) waves of the transmitral and transtricuspid flow velocity waveforms. The left and right atrial storage fractions (LASF, RASF), indexes of atrial reservoir function, were determined as the ratios of the atrial storage volume to the ventricular stroke volume; (Sa - rAa)/(Sa - rAa + Da). The left and right atrial active contraction fractions (LAACF, RAACF), indexes of atrial active transport function, were also determined as the ratios of the atrial active contraction volume to the left ventricular stroke volume; Aa/(Ea + Aa). These indices were evaluated periodically in 12 patients with non-valvular chronic atrial fibrillation before and 1-4 days after direct current cardioversion of atrial fibrillation; in 8 of the patients, the indices were also evaluated 1-3 months after the cardioversion. An additional 10 patients in sinus rhythm served as controls. Both the LASF and RASF were low during atrial fibrillation; the values increased significantly 14 days after successful cardioversion (P < 0.01 P < 0.01), and continued to increase at 1-3 months. The LASF and RASF values 1-3 months after cardioversion were comparable to those in control subjects. Both the LAACF and RAACF also increased significantly from 1-4 days to 1-3 months after cardioversion (P < 0.05, P < 0.01), becoming comparable to those in control subjects. During the 3 months after successful cardioversion of non-valvular chronic atrial fibrillation, left and right atrial reservoir function and left and right atrial active transport function increased progressively, becoming comparable to values in the control subjects.