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AbstractBackground:The prognostic value of cardiopulmonary exercise testing (CPET) variables for major cardiovascular events in patients with heart failure (HF) is widely established. However, the prognostic value of these variables as predictors of appropriate implantable cardioverter-defibrillator (ICD) therapies has not been sufficiently well addressed. This study aimed to evaluate CPET variables such as peak oxygen uptake (VO2peak), relationship between change in minute ventilation (VE) and carbon dioxide output (VCO2) during incremental exercise (VE/VCO2slope) and exercise-related periodic breathing (EPB) as appropriate ICD therapy predictors in HF patients.Methods:We retrospectively assessed 61 HF patients who underwent CPET and had ICD implanted for primary prevention. Patients were followed for 767 ± 601 days. Primary outcome was appropriate ICD-delivered therapy, either anti-tachycardia pacing (ATP) or shock.Results:The sample consisted mostly of male patients (65.6%), with severe ventricular dysfunction (mean left ventricular ejection fraction (LVEF) 27 ± 6%). The primary outcome occurred in 20 patients (32%). There were no significant differences in VO2peak (17.7 ± 4.1 and 16.9 ± 4.5 mL/kg/min), VE/VCO2slope (39.7 ± 8.4 and 39.6 ± 10.2) or EPB prevalence (20% and 19.5%) in patients with or without appropriate ICD therapy. According to Cox regression analysis, none of the CPET variables were significant predictors of appropriate ICD therapy.Conclusions:In this cohort study of HF patients, CPET variables did not predict appropriate ICD therapies. Further studies with large number of patients are warranted to address this issue.

IMPORTANCE: The presumed proarrhythmic action of caffeine is controversial. Few studies have assessed the effect of high doses of caffeine in patients with heart failure due to left ventricular systolic dysfunction at high risk for ventricular arrhythmias. OBJECTIVE: To compare the effect of high-dose caffeine or placebo on the frequency of supraventricular and ventricular arrhythmias, both at rest and during a symptom-limited exercise test. DESIGN, SETTING, AND PARTICIPANTS: Double-blinded randomized clinical trial with a crossover design conducted at the heart failure and cardiac transplant clinic of a tertiary-care university hospital. The trial included patients with chronic heart failure with moderate-to-severe systolic dysfunction (left ventricular ejection fraction <45%) and New York Heart Association functional class I to III between March 5, 2013, and October 2, 2015. INTERVENTIONS: Caffeine (100 mg) or lactose capsules, in addition to 5 doses of 100 mL decaffeinated coffee at 1-hour intervals, for a total of 500 mg of caffeine or placebo during a 5-hour protocol. After a 1-week washout period, the protocol was repeated. MAIN OUTCOMES AND MEASURES: Number and percentage of ventricular and supraventricular premature beats assessed by continuous electrocardiographic monitoring. RESULTS: We enrolled 51 patients (37 [74%] male; mean [SD] age, 60.6 [10.9] years) with predominantly moderate-to-severe left ventricular systolic dysfunction (mean [SD] left ventricular ejection fraction, 29% [7%]); 31 [61%] had an implantable cardioverter-defibrillator device. No significant differences between the caffeine and placebo groups were observed in the number of ventricular (185 vs 239 beats, respectively; P = .47) and supraventricular premature beats (6 vs 6 beats, respectively; P = .44), as well as in couplets, bigeminal cycles, or nonsustained tachycardia during continuous electrocardiographic monitoring. Exercise test–derived variables, such as ventricular and supraventricular premature beats, duration of exercise, estimated peak oxygen consumption, and heart rate, were not influenced by caffeine ingestion. We observed no increases in ventricular premature beats (91 vs 223 vs 207 beats, respectively) in patients with higher levels of plasma caffeine concentration compared with lower plasma levels (P = .91) or with the placebo group (P = .74). CONCLUSIONS AND RELEVANCE: Acute ingestion of high doses of caffeine did not induce arrhythmias in patients with systolic heart failure and at high risk for ventricular arrhythmias. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT02045992

Ablation of atrial flutter has been shown to be safe and effective, but little is known about the effect of the ablation procedure on AV nodal function. In 28 patients (21 males, mean 55±14 yo, 13 with coronary artery disease) who underwent successful ablation of typical atrial flutter, including 19 (68%) also presenting with atypical flutter, retrograde and antegrade AV nodal function were measured before and after the procedure. RF ablation was achieved by applying linear lesions across the medial isthmus of the right atrium from the tricuspid annulus to coronary sinus ostium and then to the inferior vena cava ostium. Additional linear lesions were also made across the middle portion of the isthmus from the tricuspid annulus to the inferior vena cava ostium. This ablation approach should effectively isolate the posterior input generated by the crista terminalis to the AV node, Ablation was successful in all patients and no patient developed complete heart block. Incidental dual AV nodal function was eliminated in 3 of 4 patients. Pre- and post-ablation AV nodal function are as follows:PAAHHVAnt ERPAnt FRPAnt BlockRet BlockPre RF45±10B4±3651±9337±73444±61365±97476±178PostRF47±1187±3250±9321±79432±62354±81471±179p value0.40.760.920.670.70.60.94