Two-staged biatrial linear and focal ablation to restore sinus rhythm in patients with refractory chronic atrial fibrillation: procedure experience and follow-up beyond 1 year

Recent observations regarding the mechanisms of chronic atrial fibrillation (CAF) plus a few encouraging clinical reports have created a paradigm shift regarding treatment strategies and the potential for restoring normal sinus rhythm (NSR) utilizing available catheter-based ablation techniques. The initial and late follow-up clinical experience with a two-staged biatrial linear and focal radiofrequency ablation (BALF I, II) procedure to restore NSR in patients with CAF are described. Pre-BALF management included confirming drug refractoriness and optimizing anticoagulation therapy. BALF I and II were preceded by transesophageal echocardiography to exclude thrombus. Femoral venous catheters were placed in the left atrium and the right atrium with extensive left atrial mapping, ablation (linear and focal) and more limited right atrial ablation. Localized electrogram recordings demonstrated rapid, localized, stable focal driving rotors (FDRs) in the left atrium (nine patients) and in the right atrium (one patient). Atrial or intraatrial tachycardia (IAT) commonly recurred after BALF I. BALF II addresses these recurrences by repeat mapping and ablation techniques. There were no thromboembolic complications. Two patients developed pericardial tamponade that responded to medical management. Of the 11 patients with late follow-up data, 9 have NSR, atrial function, and are no longer experiencing CAF. Left atrial ablation lines decrease continuous electrogram activity, probably isolate portions of the atrium, and unmask FDRs. Focal and linear ablations appear helpful in transforming CAF to NSR. FDRs are commonly localized to pulmonary vein ostium, trabeculated portions of the atrium, and left atrial appendage.

Congestive heart failure. Current and future strategies to decrease mortality

The prevalence of and mortality from congestive heart failure increase with advancing age. The most important prognostic indicators are exercise tolerance and left ventricular function. Currently, drug treatment consists of digitalis, diuretics, and ACe inhibitors. Future management may include medications to modulate the extracardiac mechanisms of decompensation and newer surgical techniques to assist or replace the failing heart.

Inotropic effects of angiotensin II on human cardiac muscle in vitro

The direct effects of angiotensin II (Ang II) on human cardiac muscle were investigated using isolated trabecular muscles from failing and functionally normal hearts. Atrial and ventricular trabeculae were studied. Results demonstrated a positive inotropic effect of Ang II on human cardiac muscle. Comparison of the effects of Ang II among groups indicated that the responsiveness tended to be greater in atrial and normal muscle compared with failing muscle. Results of this study also demonstrated heterogeneity in the responsiveness to Ang II among human muscles, which was not correlated with patient age, sex, diagnosis, prior treatment with angiotensin converting enzyme inhibitor, or heart function. A significant correlation between response to Ang II and response to isoproterenol was demonstrated in failing ventricular trabeculae, which may suggest that defects in beta-adrenergic responsiveness in the failing human ventricle are accompanied by a loss of responsiveness to Ang II. Studies were extended to the Syrian cardiomyopathic hamster and its control. A dose-dependent inotropic response occurred in normal hamster ventricular muscle but was significantly diminished in cardiomyopathic muscle. Ang II did not shorten the timing of contraction, and pretreatment with adrenergic-blocking agents did not shift the dose-response curve, indicating that the response was not cyclic AMP mediated. This study demonstrates for the first time that Ang II can exert an inotropic effect directly on human cardiac muscle and confirms that there is a direct effect of Ang II on hamster cardiac muscle. The study further suggests, however, that the inotropic response to Ang II in cardiac muscle is heterogeneous and may be diminished by heart failure.

Changes in hemodynamics and myocardial contractility during chronic sodium depletion in conscious dogs

Chronic sodium depletion has been reported to decrease ejection fraction in anesthetized dogs. We tested the hypothesis that this reduction in cardiac performance is due to either hemodynamic or humoral factors. Seven mongrel dogs were fed a low sodium diet (less than 2 mEq Na+ per day) for 5 weeks. Echocardiographic and radionuclide techniques were used to monitor cardiac function. There was a gradual but significant (p less than 0.01) decrease in ejection fraction from 61 +/- 7% (SD) at baseline to 47 +/- 8% after 5 weeks of sodium depletion in association with a fall in left ventricular end-diastolic volume. Ejection fraction did not change in five control dogs fed 55 mEq Na+ per day throughout the 5-week follow-up period. Myocardial contractility did not change in either salt-depleted or control dogs. Plasma norepinephrine levels in the coronary sinus were twice as high in salt-depleted as in control dogs, but there were no significant differences in arterial norepinephrine concentration between the two groups. Therefore, we concluded that reduced ejection fraction during sodium depletion resulted from hemodynamic changes (decreased preload). The excess available norepinephrine failed to increase myocardial contractility, suggesting a dysfunction at the cardiac adrenergic neuroeffector junction.