Sohail Hassan

Clinical significance of early recurrences of atrial fibrillation after pulmonary vein isolation

OBJECTIVES The purposes of this study were to describe the prevalence of early recurrences of atrial fibrillation (ERAF) that occur within two weeks after pulmonary vein (PV) isolation, and to determine whether ERAF is predictive of long-term outcome after PV isolation. BACKGROUND Atrial fibrillation (AF) sometimes recurs within days after PV isolation and may prompt an early repeat intervention. METHODS Segmental PV isolation was performed using radiofrequency energy in 110 consecutive patients (mean age 53 +/- 11 years) with paroxysmal (93 patients) or persistent (17 patients) AF. Three to four PVs were targeted for isolation in all patients. Pulmonary vein isolation was complete in 338 of the 358 PVs that were targeted (94%). RESULTS Early recurrences of AF occurred in 39 of 110 patients (35%) at a mean of 3.7 +/- 3.5 days after the procedure. The prevalence of ERAF was similar in patients with paroxysmal and persistent AF (33% and 47%, respectively, p = 0.4). Beyond the first two weeks, at 208 +/- 125 days of follow-up, 60 of the 71 patients without ERAF (85%) and 12 of the 39 patients with ERAF (31%) were free of recurrent AF in the absence of antiarrhythmic drug therapy (p < 0.001). CONCLUSIONS Early recurrences of AF occur in approximately 35% of patients within two weeks after isolation of three to four PVs, and are associated with a lower long-term success rate than in patients without ERAF. However, approximately 30% of patients with ERAF have no further symptomatic AF during long-term follow-up. Therefore, temporary antiarrhythmic drug therapy may be more appropriate than early repeat ablation in patients with ERAF.

Segmental Ostial Ablation to Isolate the Pulmonary Veins During Atrial Fibrillation Feasibility and Mechanistic Insights

Background—The purpose of this study was to determine the feasibility and mechanistic implications of segmental pulmonary vein (PV) ostial ablation during atrial fibrillation (AF). Methods and Results—Forty consecutive patients underwent PV isolation for AF. Among 125 PVs targeted for isolation, ablation was performed during AF in 70 veins and during sinus rhythm in 55 veins. A decapolar Lasso catheter was positioned near the ostium. During AF, ostial ablation was performed near the Lasso catheter electrodes that recorded a tachycardia with a cycle length shorter than in the adjacent left atrium. During sinus rhythm, ostial ablation was guided by PV potentials. Complete PV isolation was achieved in 70 PVs (100%) ablated during AF and in 53 PVs (96%) ablated during sinus rhythm (P =0.4). The mean durations of radiofrequency energy needed for isolation were 7.4±4.4 and 5.2±3.9 minutes during AF and sinus rhythm, respectively (P <0.01). Before ablation, an immediate recurrence of AF (IRAF), occurred after cardioversion in 18 of 40 patients, and IRAF was consistently abolished by PV isolation. The probability of AF termination during isolation of a PV was directly related to the extent of tachycardia in that vein. As more PVs were isolated, induction of persistent AF by rapid pacing became less likely. Conclusions—Segmental ostial ablation guided by PV tachycardia during AF is feasible and as efficacious as during sinus rhythm. The responses to cardioversion, ablation, and rapid pacing observed in this study imply that IRAF is triggered by the PVs and that PV tachycardias may play an important role in the perpetuation of AF.

Mechanistic Significance of Intermittent Pulmonary Vein Tachycardia in Patients with Atrial Fibrillation

Pulmonary Vein Tachycardia. Introduction: The significance of intermittent tachycardia within a pulmonary vein (PV) during an episode of atrial fibrillation (AF) is unclear. The aim of this study was to determine the role that intermittent PV tachycardias play in AF.

SA Gene Expression in the Proximal Tubule of Normotensive and Hypertensive Rats

Previous studies have shown that the SA gene is expressed at higher levels in the kidney of genetically hypertensive rats than in control strains and that in hybrid crosses of genetically hypertensive rats and normotensive controls, markers in or close to the SA gene cosegregate with blood pressure. The present studies examine the localization of the SA gene product in the kidney by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). cDNA was prepared from microdissected nephron segments from Sprague-Dawley (SD) rats, spontaneously hypertensive rats (SHRs), and Wistar-Kyoto (WKY) rats, and RT-PCR was performed using specific primers. In all three strains, SA gene mRNA was found to be abundantly expressed in proximal tubules. SA PCR product was occasionally detected at approximately 100-fold lower abundance in glomeruli, while no signal was obtained from the collecting duct, thick ascending limb of the loop of Henle, or arcuate artery. Within the proximal tubule of normotensive rats, distribution of SA mRNA was found to be strain dependent: in SD rats it was expressed at high levels in the proximal convoluted tubule, whereas in WKY rats it was restricted to the proximal straight tubule. In SHRs, SA PCR product was detected along the entire proximal tubule. Induction of hypertension by renal artery clamping (two-kidney, one-clamp Goldblatt model) did not alter the pattern of expression observed in the SD rat. These results indicate that an extension of SA gene expression to the full length of the proximal tubule accompanies spontaneous hypertension and that in nonhypertensive animals the pattern of gene product expression is more restricted but shows substantial strain variability.

Randomized Comparison of Bipolar versus Unipolar Plus Bipolar Recordings During Segmental Ostial Ablation of Pulmonary Veins

Unipolar vs Bipolar Electrograms. Introduction: Segmental ostial ablation to isolate pulmonary veins is guided by pulmonary vein potentials. The aim of this prospective randomized study was to compare the utility of unipolar plus bipolar electrograms versus only bipolar electrograms as a guide for segmental ablation to isolate the pulmonary veins in patients with atrial fibrillation.

Chronic Kidney Disease and Mortality in Implantable Cardioverter-Defibrillator Recipients

Incidence of sudden cardiac death (SCD) in end-stage renal disease (ESRD) remains high. Limited data is available about whether implantable cardioverter-defibrillators (ICDs) can prevent arrhythmic death in patients with chronic kidney disease (CKD). The purpose of this retrospective study was to determine the impact of CKD on all-cause and sudden cardiac death in ICD recipients. We evaluated 441 consecutive patients who underwent ICD implantation at our center between 1994 and 2002. We found that mortality rate was higher in patients with eGFR <60 mL/min and those with ESRD on hemodialysis (43%, n = 69/162 and 54%, n = 12/22, resp.) than in patients with eGFR ≥60 mL/min (23%, n = 58/257; P < .0005). The SCD rate was also higher in the patients with ESRD (50%) than in CKD patients not on dialysis (10.2%; P < .0005). Mortality rate for single-chamber ICDs was 56.8% in comparison with dual-chamber ICDs (38.1%) and for biventricular ICDs (5.0%) (P < .0005).

Conversion of Atrial Fibrillation to Sinus Rhythm During Treatment With Intravenous Esmolol or Diltiazem: A Prospective, Randomized Comparison:

Prior studies have suggested that intravenous diltiazem reduces the probability of spontaneous conversion of atrial fibrillation (AF) to sinus rhythm in the electrophysiology laboratory and in patients with postoperative AF. Whether diltiazem exerts the same effect in patients presenting to the emergency department (ED) with spontaneous AF is unclear. Fifty patients presenting to the ED with new-onset or paroxysmal AF and a rapid ventricular rate (>100 beats per minute) were randomly assigned to receive intravenous diltiazem or esmolol during the first 24 hours of presentation. Conversion to sinus rhythm occurred in 10 patients (42%) in the diltiazem group compared with 10 patients (39%) in the esmolol group (P = 1.0). Diltiazem does not decrease the likelihood of spontaneous conversion of AF to sinus rhythm in the ED setting.

Rate-dependent effect of verapamil on atrial refractoriness.

OBJECTIVES The purpose of this study was to determine whether verapamil has rate-dependent effects on the atrial effective refractory period (AERP). BACKGROUND Block of calcium current (I(Ca)) and rapid component of the delayed rectifier potassium current (I(Kr)) by verapamil is frequency-dependent. This may result in variable effects of verapamil on the AERP, depending on the rate. METHODS The subjects of this study were 30 adults with a mean age of 45 +/- 13 years who did not have structural heart disease. In 20 subjects, the AERP was measured at basic drive cycle lengths (BDCLs) of 650 to 250 ms, in 50 ms decrements, before and after infusion of 0.1 mg/kg verapamil. The effective refractory periods (ERPs) were measured in the setting of autonomic blockade in 10 subjects and without autonomic blockade in 10 subjects. Ten subjects served as a control group and received a saline infusion instead of verapamil. RESULTS Verapamil significantly prolonged the AERP at BDCLs of 650 to 500 ms (p < 0.01 or p < 0.05) and significantly shortened the ERP at BDCLs of 300 and 250 ms (p < 0.01). In the control group, there were no significant differences between the baseline and post-saline measurements of ERP. CONCLUSIONS Verapamil prolongs AERP at slow rates and shortens AERP at rapid rates. These findings are consistent with a predominant effect on I(Ca) at rapid rates and a predominant effect on I(Kr) at slow rates.

Comparison of amiodarone versus ibutilide for the prevention of immediate recurrences of atrial fibrillation during pulmonary vein isolation.

During segmental ostial ablation for pulmonary vein isolation, pulmonary vein potentials are easily identified during sinus rhythm or left atrial pacing. Therefore, maintenance of atrial fibrillation (AF) during the procedure is desirable. However, cardioversion is occasionally followed by an immediate recurrence of AF. This study compared the efficacy of ibutilide and amiodarone in preventing immediate recurrences of AF in patients who underwent pulmonary vein isolation. The subjects of this study were 25 patients (mean age 56 +/- 10 years) who underwent pulmonary vein isolation for AF who had an immediate recurrence of AF within 60 seconds after 2 transthoracic cardioversions. The patients were randomized to receive an infusion of either 300 mg of amiodarone over 10 minutes or 1 mg of ibutilide over 5 minutes. Cardioversion was repeated 15 minutes after the drug infusion. If immediate recurrences of AF occurred 2 more times, the alternative study drug was administered, and cardioversion was repeated. Immediate recurrences of AF were suppressed by amiodarone in 8 of 10 patients (80%), and by ibutilide in 9 of 15 patients (60%, p = 0.4). After crossover, immediate recurrence of AF was suppressed in 2 of 6 patients (33%) by amiodarone, and in 1 of 2 patients (50%) by ibutilide (p = 0.6). Ibutilide and amiodarone, when used alone or in combination, prevented immediate recurrences of AF in 20 of 25 patients (80%). There were no adverse drug effects. Ibutilide and amiodarone were equally effective in suppressing immediate recurrences of AF. Overall, immediate recurrences of AF can be prevented by amiodarone and/or ibutilide in 80% of patients.

THANKSGIVING MEAL PARALYSIS? A RARE CASE OF THYROTOXIC PERIODIC PARALYSIS WITH CARDIAC ARREST

Thyrotoxic periodic paralysis(TPP) is an endocrinopathy related to increased Na+/K+ ATPase activity, triggered by hyperadrenergic, hyperthyroid, or hyperinsulinemic states. It is characterized by transient, recurrent episodes of flaccid muscle paralysis affecting proximal more severely than distal