Journal of Cardiovascular Electrophysiology

In December 2019, the world started to face a new pandemic situation, the severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2). Although coronavirus disease (COVID‐19) clinical manifestations are mainly respiratory, major cardiac complications are being reported. Cardiac manifestations etiology seems to be multifactorial, comprising direct viral myocardial damage, hypoxia, hypotension, enhanced inflammatory status, ACE2‐receptors downregulation, drug toxicity, endogenous catecholamine adrenergic status, among others. Studies evaluating patients with COVID‐19 presenting cardiac injury markers show that it is associated with poorer outcomes, and arrhythmic events are not uncommon. Besides, drugs currently used to treat the COVID‐19 are known to prolong the QT interval and can have a proarrhythmic propensity. This review focus on COVID‐19 cardiac and arrhythmic manifestations and, in parallel, makes an appraisal of other virus epidemics as SARS‐CoV, Middle East respiratory syndrome coronavirus, and H1N1 influenza.

Background: Chronic right ventricular pacing has been reported to promote cardiac dyssynchrony. The PAVE trial prospectively compared chronic biventricular pacing to right ventricular pacing in patients undergoing ablation of the AV node for management of atrial fibrillation with rapid ventricular rates.

Methods and Results: One hundred and eighty‐four patients requiring AV node ablation were randomized to receive a biventricular pacing system (n = 103) or a right ventricular pacing system (n = 81). The study endpoints were change in the 6‐minute hallway walk test, quality of life, and left ventricular ejection fraction. Patient characteristics were similar (64% male; age: 69 ± 10 years, ejection fraction: 0.46 ± 0.16; 83%, NYHA Class II or III). At 6 months postablation, patients treated with cardiac resynchronization had a significant improvement in 6‐minute walk distance, (31%) above baseline (82.9 ± 94.7 m), compared to patients receiving right ventricular pacing, (24%) above baseline (61.2 ± 90.0 m) (P = 0.04). There were no significant differences in the quality‐of‐life parameters. At 6 months postablation, the ejection fraction in the biventricular group (0.46 ± 0.13) was significantly greater in comparison to patients receiving right ventricular pacing (0.41 ± 0.13, P = 0.03). Patients with an ejection fraction ≤45% or with NYHA Class II/III symptoms receiving a biventricular pacemaker appear to have a greater improvement in 6‐minute walk distance compared to patients with normal systolic function or Class I symptoms.

Conclusion: For patients undergoing AV node ablation for atrial fibrillation, biventricular pacing provides a significant improvement in the 6‐minute hallway walk test and ejection fraction compared to right ventricular pacing. These beneficial effects of cardiac resynchronization appear to be greater in patients with impaired systolic function or with symptomatic heart failure.

Introduction: Patients with end‐stage heart failure and a wide QRS complex are considered candidates for cardiac resynchronization therapy (CRT). However, 20% to 30% of patients do not respond to CRT. Lack of left ventricular dyssynchrony may explain the nonresponse. Accordingly, we evaluated the presence of left ventricular dyssynchrony using tissue Doppler imaging (TDI) in 90 consecutive patients with heart failure.

Methods and Results: Ninety patients with severe heart failure (left ventricular ejection fraction <35%, New York Heart Association class III–IV) were prospectively evaluated. Based on QRS duration, 30 consecutive patients with a narrow QRS complex were included (QRS duration ≤120 ms), 30 patients with an intermediate QRS duration (120–150 ms), and 30 patients with a wide QRS complex (>150 ms). All patients underwent TDI to assess left ventricular dyssynchrony. Extensive left ventricular dyssynchrony was defined as an electromechanical delay on TDI between the septum and lateral wall, the so‐called septal‐to‐lateral delay, of >60 ms. Severe dyssynchrony was observed in 27% of patients with narrow QRS complex, 60% with intermediate QRS duration, and 70% with wide QRS complex. No relation existed between QRS duration and septal‐to‐lateral delay.

Conclusion: From 30% to 40% of heart failure patients with QRS duration >120 ms do not exhibit left ventricular dyssynchrony, which may explain the nonresponse to CRT. Alternatively, 27% of patients with heart failure and a narrow QRS complex show significant left ventricular dyssynchrony and may be candidates for CRT. (J Cardiovasc Electrophysiol, Vol. 15, pp. 544‐549, May 2004)

This report describes a fatal case of left atrial‐esophageal fistula occurring in a 72‐year‐old man after a radiofrequency catheter ablation of paroxysmal atrial fibrillation. Catheter ablation was performed around the pulmonary vein using an 8‐mm‐tip electrode (60 W or 55°C) guided by a 25‐mm circular catheter. On day 22 of follow‐up, the patient presented with seizures followed by hematemesis due to left atrial–esophageal fistula. His clinical condition deteriorated, and he died of speticemia. Thus, left atrial–esophageal fistula is a sever complication of radiofrequency catheter ablation of the left atrial posterior wall. (J Cardiovasc Electrophysiol, Vol. 15, pp. 960‐962, August 2004)

New Classification of Atrial Tachycardia. Regular atrial tachycardias classically are classified into flutter or tachycardia, depending on the rate and presence of a stable baseline on the ECG. However, current understanding of electrophysiology atrial tachycardias makes this classification obsolete, because it does not correlate with mechanisms. The proposed classification is based on electrophysiologic mechanisms, defined by mapping and entrainment. Radiofrequency ablation of a critical focus or isthmus can afford proof. Focal tachycardias are characterized by radial spread of activation and endocardial activation not covering the whole cycle. Ablation of the focus of origin interrupts the tachycardia. The mechanism of focal firing is difficult to ascertain by clinical methods. Macroreentrant tachycardias are characterized by circular patterns of activation that cover the whole cycle. Fusion can be shown during entrainment on the ECG or by multiple endocardial recordings. Ablation of a critical isthmus interrupts the tachycardia. Macroreentry can occur around normal structures (terminal crest, eustachian ridge) or around atrial lesions. The anatomic bases of these tachycardias must be defined, to guide appropriate treatment. Atrial flutter is a mere description of continuous undulation on the ECG, and only some strictly defined typical flutter patterns correlate with right atrial macroreentry bounded by the tricuspid valve, terminal crest, and caval vein orifices. This classification should be considered open, as some classically described tachycardias, such as reentrant sinus tachycardia, inappropriate sinus tachycardia, and type II atrial flutter, cannot be classified accurately. Furthermore, the possibility of fibrillatory conduction makes the limits with atrial fibrillation still ill defined.

RF Ablation. Radiofrequency (RF) catheter ablation has become the treatment of choice for many symptomatic cardiac arrhythmias. It is presumed that the primary cause of tissue injury by RF ablation is thermally mediated, resulting in a relatively discrete homogeneous lesion. The mechanism by which RF current heats tissue is resistive heating of a narrow rim (< 1 mm) of tissue that is in direct contact with the ablation electrode. Deeper tissue heating occurs as a result of passive heat conduction from this small region of volume heating. Lesion size is proportional to the temperature at the electrode‐tissue interface and the size of the ablation electrode. Temperatures above 50°C are required for irreversible myocardial injury, but temperatures above 100°C result in coagulum formation on the ablation electrode, a rapid rise in electrical impedance, and loss of effective tissue heating. Lesion formation is also dependent on optimal electrode‐tissue contact and duration of RF delivery. Newer developments in RF ablation include temperature monitoring, longer ablation electrodes coupled to high‐powered RF generators, and novel ablation electrode designs.

Risk for Permanent Pacemaker After Transcatheter Aortic Valve Implantation.

Background: Permanent pacemaker (PM) requirement is a known complication after transcatheter aortic valve implantation (TAVI). There are, however, no systematic data concerning this complication.

Objective: To determine the incidence and potential predictors of permanent PM requirement after TAVI based on published literature.

Methods: We conducted a MEDLINE search to identify potentially relevant literature dealing with PM requirement after TAVI. Data were collected on paper extraction forms by 2 independent investigators.

Results: There were 32 relevant published studies comprising data of 5,258 patients without an implanted PM before TAVI. An Edwards‐Sapiens® prosthesis (ESP) was implanted in 2,887 patients, whereas 2,371 patients received a CoreValve® prosthesis (CVP). The crude incidence of PM implantation after TAVI was 15%. Six hundred and fourteen of 2,371 (25.8%) CVP patients and 189 of the 2,887 (6.5%) ESP patients had to receive a permanent PM (odds ratio [OR] 4.91, 95% confidence interval [CI] 4.12–5.86, P < 0.001). Presence of right bundle branch block (RBBB) before TAVI was a significant predictor for development of complete atrioventricular (AV) block and subsequent PM need (OR 1.358, 95% CI 1.001–1.841, P = 0.02). More than 90% of all AV‐block requiring PM implantation occurred immediately or within 7 days after TAVI.

Conclusion: Patients undergoing TAVI with implantation of CVP are at significantly higher risk for development of AV block and subsequent need for permanent PM, particularly if RBBB preexists. Since AV block occurs in >90% within the first week after the procedure, careful monitoring should be performed for at least 7 days after TAVI.

PV Stenosis after AF Ablation. Introduction: Elimination of the initiating focus within the pulmonary vein (PV) using radiofrequency (RF) catheter ablation is a new treatment modality for treatment of drug‐refractory atrial fibrillation. However, information on the long‐term safety of RF ablation within the PV is limited.

Methods and Results: In 102 patients with drug‐refractory atrial fibrillation and at least one initiating focus from the PV, series transesophageal echocardiography was performed to monitor the effect of RF ablation on the PV. There were 66 foci in the right upper PV and 65 foci in the left upper PV. Within 3 days of ablation, 26 of the ablated right upper PVs (39%) had increased peak Doppler flow velocity (mean 130 ± 28 cm/sec, range 106 to 220), and 15 of the ablated left upper PVs (23%) had increased peak Doppler flow velocity (mean 140 ± 39 cm/sec, range 105 to 219). Seven patients had increased peak Doppler flow velocity in both upper PVs. No factor (including age, sex, site of ablation, number of RF pulses, pulse duration, and temperature) could predict PV stenosis after RF ablation. Three patients with stenosis of both upper PVs experienced mild dyspnea on exertion, but only one had mild increase of pulmonary pressure. There was no significant change of peak and mean flow velocity and of PV diameter in sequential follow‐up studies up to 16 (209 ± 94 days) months.

Conclusion: Focal PV stenosis is observed frequently after RF catheter ablation applied within the vein, but usually is without clinical significance. However, ablation within multiple PVs might cause pulmonary hypertension and should be considered a limiting factor in this procedure.