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Objectives The study assessed whether heart rate (HR) reduction following an exercise stress test (ExStrT), an easily quantifiable marker of vagal reflexes, might identify high-and low-risk long QT syndrome (LQTS) type 1 (LQT1) patients. Background Identification of LQTS patients more likely to be symptomatic remains elusive. We have previously shown that depressed baroreflex sensitivity, an established marker of reduced vagal reflexes, predicts low probability of symptoms among LQT1. Methods We studied 169 LQTS genotype-positive patients < 50 years of age who performed an ExStrT with the same protocol, on and off beta-blockers including 47 South African LQT1 patients all harboring the KCNQ1-A341V mutation and 122 Italian LQTS patients with impaired (I-Ks-, 66 LQT1) or normal (I-Ks +/-, 50 LQT2 and 6 LQT3) I-Ks current. Results Despite similar maximal HR and workload, by the first minute after cessation of exercise the symptomatic patients in both IKs-groups had a greater HR reduction compared with the asymptomatic (19 +/- 7 beats/min vs. 13 +/- 5 beats/min and 27 +/- 10 beats/min vs. 20 +/- 8 beats/min, both p = 0.009). By contrast, there was no difference between the I-Ks +/- symptomatic and asymptomatic patients (23 +/- 9 beats/min vs. 26 +/- 9 beats/min, p = 0.47). LQT1 patients in the upper tertile for HR reduction had a higher risk of being symptomatic (odds ratio: 3.28, 95% confidence interval: 1.3 to 8.3, p = 0.012). Conclusions HR reduction following exercise identifies LQT1 patients at high or low arrhythmic risk, independently of beta-blocker therapy, and contributes to risk stratification. Intense exercise training, which potentiates vagal reflexes, should probably be avoided by LQT1 patients.

We assessed the influence of clinically significant mitral regurgitation (MR) on clinical-echocardiographic response and outcome in heart failure (HF) patients treated with a biventricular defibrillator (cardiac resynchronization therapy defibrillator [CRT-D]). METHODS AND RESULTS: A total of 659 HF patients underwent successful implantation of CRT-D and were enrolled in a multicenter prospective registry (median follow-up of 15 months). Following baseline echocardiographic evaluation, patients were stratified into two groups according to the severity of MR: 232 patients with more than mild MR (Group MR+: grade 2, 3, and 4 MR) versus 427 patients with mild (grade 1) or no functional MR (Group MR-). On 6- and 12-month echocardiographic evaluation, MR was seen to have improved in the vast majority of MR+ patients, while it remained unchanged in most MR- patients. On 12-month follow-up evaluation, a comparable response to CRT was observed in the two groups, in terms of the extent of left ventricular reverse remodeling and combined clinical and echocardiographic response. During long-term follow-up, event-free survival did not differ between MR+ and MR- patients, even when subpopulations of patients with ischemic heart disease and with dilated cardiomyopathy were analyzed separately. On multivariate analysis, the only independent predictor of death from any cause was the lack of β-blocker use. CONCLUSIONS: This observational analysis supports the use of CRT-D in HF patients with clinically significant MR; MR had no major influence on patient outcome.

Aims To analyse the effectiveness of cardiac resynchronization therapy (CRT) in patients with valvular heart disease (a subset not specifically investigated in randomized controlled trials) in comparison with ischaemic heart disease or dilated cardiomyopathy patients. Methods and results Patients enrolled in a national registry were evaluated during a median follow-up of 16 months after CRT implant. Patients with valvular heart disease treated with CRT ( n = 108) in comparison with ischaemic heart disease ( n = 737) and dilated cardiomyopathy ( n = 635) patients presented: (i) a higher prevalence of chronic atrial fibrillation, with atrioventricular node ablation performed in around half of the cases; (ii) a similar clinical and echocardiographic profile at baseline; (iii) a similar improvement of LVEF and a similar reduction in ventricular volumes at 6–12 months; (iv) a favourable clinical response at 12 months with an improvement of the clinical composite score similar to that occurring in patients with dilated cardiomyopathy and more pronounced than that observed in patients with ischaemic heart disease; (v) a long-term outcome, in term of freedom from death or heart transplantation, similar to patients affected by ischaemic heart disease and basically more severe than that of patients affected by dilated cardiomyopathy. Conclusion In ‘real world’ clinical practice, CRT appears to be effective also in patients with valvular heart disease. However, in this group of patients the outcome after CRT does not precisely overlap any of the two other groups of patients, for which much more data are currently available.

Background: Few data exist on the long-term changes and the prognostic value of heart rate variability (HRV) assessed by implanted devices in heart failure (HF) patients treated with resynchronization therapy (CRT). Aims: To analyze the long-term changes in the standard deviation of 5-minute median atrial–atrial sensed intervals (SDANN), and assess its role in predicting CRT efficacy and major cardiovascular events. Methods and results: We included 509 consecutive patients implanted with CRT devices. At 12-month follow-up, 44 patients had died and 86 patients had at least one HF hospitalisation. A significant increase in SDANN occurred after 4 weeks of CRT (from 69±22 ms to 82±27 ms, p

Paroxysmal atrial fibrillation is often initiated by foci in the pulmonary veins (PVs); the junction between the PVs and the left atrium (LA) has become the target of radiofrequency (RF) ablation performed to isolate the PVs. Ectopic atrial beats originating from the PVs propagate to the LA with a characteristically long conduction time, often with a conduction delay or block within the PV or at the PV-LA junction. However, details about the conduction properties within the PVs and across the PV-LA junction are still scanty. We report a unique case of LA-PV decremental conduction caused by RF applications. New insights into the electroanatomical characteristics of the PV-LA junction are provided. The present report demonstrates, for the first time in humans, that decremental conduction may be related to the progressive damage of the conducting myocardial bundle due to RF energy applications.

It has been suggested that a reentrant circuit confined to the posterior extensions of the atrioventricular node underlies both fast-slow and slow-slow types of atrioventricular nodal reentrant tachycardia (AVNRT). According to this hypothesis the fast-slow reentrant circuit would be formed by two slow pathways, located in the rightward and leftward posterior extension of the atrioventricular node. Thus, the fast pathway would act as a bystander with respect to the reentrant circuit. We describe the case of a 40-year-old woman with several episodes of palpitations unresponsive to antiarrhythmic drugs. The ECG during symptoms showed a narrow QRS tachycardia with a long ventriculo-atrial interval and a negative P wave in the inferior leads. Electrophysiological study showed the inducibility of a slow-slow AVNRT which rapidly shifted to a fast-slow AVNRT without any change in the duration of the tachycardia cycle. Our observation is in agreement with the hypothesis that the fast-slow reentrant circuit consists of two slow pathways with the fast pathway acting as a bystander.

Background The debate on the diagnostic value of high intercostal spaces (ICSs) and of the number of diagnostic leads in Brugada syndrome (BrS) has been settled by a recent expert consensus statement. Objective To test the validity, and the underlying anatomy, of the new electrocardiographic (ECG) diagnostic criteria using echocardiographic, molecular, and clinical evidence in 1 clinical study population with BrS. Methods We analyzed 114 patients with BrS and with a spontaneous or drug-induced type 1 ECG pattern recorded in 1 or more right precordial leads in fourth, third, and second ICSs. The right ventricular outflow tract (RVOT) was localized by using echocardiography. All probands were screened on the SCN5A gene. Results The percentage of mutation carriers (MCs) and the event rate were similar regardless of the diagnostic ICS (fourth vs high ICSs: MCs 23% vs 19%; event rate 22% vs 28%) and the number of diagnostic leads (1 vs 2: MCs 20% vs 22%; event rate 22% vs 27%). The concordance between RVOT anatomical location and the diagnostic ICSs was 86%. The percentage of the diagnostic ECG pattern recorded was significantly increased by the exploration of the ICSs showing RVOT by echocardiography (echocardiography-guided approach vs conventional approach 100% vs 43%; P