Ventricular arrhythmias in patients with implanted ventricular assist devices: a contemporary review.

Ventricular arrhythmia (VA) is a significant factor in the clinical management of patients with congestive heart failure (CHF). Understanding the implications of VA in ventricular assist device-supported CHF patients is critical to appropriate clinical decision making in this special population. This article details research findings on this topic, and attempts to link them to practical patient management strategies.

Termination of macroreentrant atrial arrhythmias by pacing stimuli without global propagation.

BACKGROUND: Electrical stimulation during ventricular tachycardia resulting in tachycardia termination without global propagation (TWGP) is a well-recognized phenomenon. However, there is a paucity of literature showing a similar phenomenon in atrial arrhythmias. OBJECTIVE: The purpose of the study was to evaluate the significance of TWGP in atrial arrhythmias. METHODS: Electrophysiological studies performed from 2000 to 2019 at Methodist Hospital, Indiana University were reviewed retrospectively. Thirty-four patients were identified in whom stimulation during atrial tachycardia/flutter resulted in TWGP. RESULTS: Of the 34 patients, 12 (29%) had cavotricuspid isthmus (CTI)-dependent atrial flutter and 22 (71%) had other atrial arrhythmias during which TWGP was seen. Mean age of the population was 53 ± 13 years; and 68% were male. Previous catheter ablation for atrial fibrillation, atrial flutter, or other atrial tachyarrhythmias had been performed in 70.5%, and 44% previously had undergone cardiac surgery involving the atria. Congenital heart disease was present in 20.5%; 3 patients were status post lung transplant. Mean cycle length of atrial arrhythmia in which TWGP was seen was 317 ± 76 ms. The sites at which TWGP was seen reproducibly were highly specific for successful termination of the arrhythmias with radiofrequency energy. The arrhythmia circuits were 12 CTI-dependent atrial flutter, 11 left atrial macroreentrant atrial tachycardia (MRAT), 1 involving both left and right atria, and 8 were other right atrial MRAT. CONCLUSION: Termination of macroreentrant atrial arrhythmias by pacing stimuli without global propagation identifies a narrow diastolic isthmus at which catheter ablation is highly effective.

Mapping and Ablation of Ventricle Arrhythmia in Patients with Left Ventricular Assist Devices.

Ventricular arrhythmias (VA) constitute well-known problems in patients with left ventricular assist devices (LVADs), with incidence ranging from 18% to as high as 52%. Catheter ablation has become a common therapeutic intervention to treat drug-refractory VA, particularly with the increase and more widespread use of durable LVADs to bridge patients to transplantation or as destination therapy. In this article, we focus on etiology, mechanisms, periprocedural management, and mapping and ablation techniques in patients with LVADs and VA.

Subcutaneous nerve activity and mechanisms of sudden death in a rat model of chronic kidney disease.

BACKGROUND: The mechanisms of sudden death in chronic kidney disease (CKD) remain unclear. OBJECTIVE: The purpose of this study was to test the hypotheses that subcutaneous nerve activity (SCNA) can be used to estimate sympathetic tone in ambulatory rats and that abrupt reduction of SCNA precedes the spontaneous arrhythmic death of Cy/+ rats. METHODS: Radiotransmitters were implanted in ambulatory normal (N = 6) and Cy/+ (CKD; N = 6) rats to record electrocardiogram and SCNA. Two additional rats were studied before and after chemical sympathectomy with 6-hydroxydopamine. RESULTS: In normal rats, the baseline heart rate (HR) and SCNA were 351 ± 29 bpm and 5.12 ± 2.97 mV·s, respectively. SCNA abruptly increased HR by 4.31% (95% confidence interval 4.15%-4.47%). In comparison, the CKD rats had reduced baseline HR (336 ± 21 bpm, P < .01) and SCNA (4.27 ± 3.19 mV·s, P < .01). When SCNA was observed, HR increased by only 2.48% (confidence interval 2.29%-2.67%, P < .01). All Cy/+ rats died suddenly, preceded by sinus bradycardia, advanced (second- and third-degree) AV block (N = 6), and/or ventricular tachycardia or fibrillation (N = 3). Sudden death was preceded by a further reduction of SCNA (3.22 ± 2.86 mV·s, P < .01) and sinus bradycardia (243 ± 55 bpm, P < .01). Histologic studies in CKD rats showed myocardial calcification that involved the conduction system. Chemical sympathectomy resulted in progressive reduction of SCNA over 7 days. CONCLUSION: SCNA can be used to estimate sympathetic tone in ambulatory rats. CKD is associated with reduced HR response to SCNA and conduction system diseases. Abrupt reduction of sympathetic tone precedes AV block, ventricular arrhythmia, and sudden death of CKD rats.