Cryoablation for AVNRT: importance of ablation endpoint criteria.

BACKGROUND: For ablation of atrioventricular nodal reentrant tachycardia (AVNRT), cryoablation has been shown to be a safe alternative to radiofrequency ablation. However, previous studies have shown a higher recurrence rate with cryoablation compared to radiofrequency ablation. OBJECTIVE: This study reviewed our experience using cryoablation for typical AVNRT using stringent endpoint criteria for slow pathway ablation, yet preserving the desirable safety profile of cryoablation. METHODS: Seventy-five consecutive cases of typical AVNRT underwent cryoablation. Ablation of the AV nodal slow pathway was performed with the goal of eliminating tachycardia, AH jump, and retrograde atrial echo beats. The primary efficacy endpoint was freedom of recurrent supraventricular tachycardia at follow-up. Analysis of AVN characteristics, number of lesions, and complications was performed. RESULTS: Seventy-two (96%) patients met the primary efficacy endpoint over an average follow-up of 34.6 (12.6-68.3) months. In patients who had complete elimination of the slow pathway, there were no recurrences. The presence of an AH jump with a single retrograde echo was highly associated with a recurrence (P = 0.0001). There were no complications, including AV conduction block. CONCLUSION: The efficacy of cryoablation for management of AVNRT can be comparable to radiofrequency energy if the suggested endpoint of elimination of tachycardia, AH jump with retrograde atrial beats, is met. Prior studies evaluating cryoablation in this setting did not require this endpoint, which could have contributed to the relatively higher rate of late recurrences.

Value of the 12-lead ECG in wide QRS tachycardia.

A wealth of useful diagnostic criteria is available to assist the health care worker in arriving at the correct diagnosis in cases of a wide QRS tachycardia (WQRST). Despite the abundance of good criteria for determining the diagnosis in cases of WQRST, they are of no use if they cannot be readily applied in an urgent clinical situation because they cannot be easily recalled or are too complex and cumbersome to use. It may be that refresher courses in the differential diagnosis of WQRST, especially for emergency physicians who are often the "first responders" to patients with WQRST, can improve physicians' diagnostic accuracy in this important disorder.

Alterations in corrected QT interval following liver transplant in patients with end-stage liver disease.

BACKGROUND: Studies have demonstrated that patients with end-stage liver disease (ESLD) often have a prolonged corrected QT interval (QTc) with variable changes in the QTc post-transplant. We sought to characterize the prevalence and degree of QTc prolongation in ESLD patients, identify risk factors for QTc prolongation, and assess changes in QTc following transplant. HYPOTHESIS: QTc interval is prolonged in ESLD patients pre-transplant due to a variety of risk factors and shortens following liver transplantation. METHODS: We conducted a retrospective, multicenter study utilizing 2 large liver-transplant databases. QTc intervals were calculated utilizing Bazett's formula. The cutoff used for prolonged QTc was 440 milliseconds for men and 460 milliseconds for women. RESULTS: There were 269 patients (169 men, 100 women) included in the final analysis. The mean pre-transplant QTc was prolonged (449.0 ms), whereas the mean post-transplant QTc shortened and was within normal limits (416.7 ms) (P < 0.0001). QTc shortened after transplant in 87% of patients. QTc normalized in 70% of patients. Age and Model for End-Stage Liver Disease (MELD) score were not predictive of prolonged QTc at baseline. CONCLUSIONS: ESLD patients often have a prolonged QTc, which frequently shortens or normalizes after transplant. Screening for prolonged QTc is warranted if medications known to prolong the QTc interval are used in ESLD patients pre-transplant. MELD score, age, and sex were not predictive of prolonged QTc at baseline.

Successful radiofrequency ablation therapy for intractable ventricular tachycardia with a ventricular assist device.

Refractory ventricular tachycardia (VT) can be a potentially life-threatening rhythm in the presence of non-ischemic dilated cardiomyopathy, particularly when it results in hemodynamic compromise. A 65-year-old man with non-ischemic cardiomyopathy was referred for multiple episodes of VT. A HeartMate left ventricular assist device (LVAD) was implanted to stabilize and control the VT. However, he had multiple episodes of VT and the frequency of ventricular arrhythmias did not improve after LVAD implantation. He required electrical cardioversion to treat each episode. On Day 41 post-operatively, radiofrequency ablation was performed. Two significant areas of scarring were identified and were successfully ablated. After ablation, he did not have significant sustained VT episodes and was discharged.

Use of nonantiarrhythmic drugs for prevention of sudden cardiac death.

It is of interest that the drugs having the most significant impact on total and sudden death mortality are those without direct electrophysiologic actions on myocardial excitable tissue. This observation may provide insight into mechanisms responsible for ventricular tachyarrhythmias causing cardiac arrest. One way to think about ventricular fibrillation is that it is the final common pathway of an electrically unstable heart. After all, the heart can "die" in only three major ways: electromechanical dissociation, asystole and heart block, and ventricular fibrillation, with the latter most common. It is the "upstream" events provoking the electrical instability that these drugs probably act upon (i.e., ischemia, fibrosis). Although we unquestionably need to pursue investigations into the electrophysiology of these ventricular tachyarrhythmias, more studies need to investigate the drugs affecting upstream events, because these agents appear to yield the greatest dividends, at least for the present. This article reviews these drugs and how they may be effective.