X. Vinolas

The rationale and design of the Shockless IMPLant Evaluation (SIMPLE) trial: A randomized, controlled trial of defibrillation testing at the time of defibrillator implantation

Defibrillation testing (DT) has been an integral part of defibrillator (implantable cardioverter defibrillator [ICD]) implantation; however, there is little evidence that it improves outcomes. Surveys show a trend toward ICD implantation without DT, which now exceeds 30% to 60% in some regions. Because there is no evidence to support dramatic shift in practice, a randomized trial is urgently needed. The SIMPLE trial will determine if ICD implantation without any DT is noninferior to implantation with DT. Patients will be eligible if they are receiving their first ICD using a Boston Scientific device (Boston Scientific, Natick, MA). Patients will be randomized to DT or no DT at the time of ICD implantation. In the DT arm, physicians will make all reasonable efforts to ensure 1 successful intraoperative defibrillation at 17 J or 2 at 21 J. The first clinical shock in all tachycardia zones will be set to 31 J for all patients. The primary outcome of SIMPLE will be the composite of ineffective appropriate shock or arrhythmic death. The safety outcome of SIMPLE will include a composite of potentially DT-related procedural complications within 30 days of ICD implantation. Several secondary outcomes will be evaluated, including all-cause mortality and heart failure hospitalization. Enrollment of 2,500 patients with 3.5-year mean follow-up will provide sufficient statistical power to demonstrate noninferiority. The study is being performed at approximately 90 centers in Canada, Europe, Israel, and Asia Pacific with final results expected in 2013.

Cardiac arrhythmias and left ventricular hypertrophy in systemic hypertension and their influences on prognosis

Left ventricular hypertrophy (LVH) is the adaptative mechanism of the heart to systolic overload of the left ventricle. Nevertheless, LVH plays a role in some complications, such as cardiac arrhythmias. Patients with LVH are more likely to develop ventricular arrhythmias than the hypertensive population without LVH. Further, the relation between left ventricular mass and ventricular arrhythmias is graded and continuous. The arrhythmias described in hypertensive patients with LVH are usually isolated premature ventricular contractions. The presence of electrocardiographic criteria of LVH represents a risk of higher incidence of sudden death, especially in men. The risk is even greater in the presence of ventricular arrhythmias. The presence of late potentials has been recently characterized as more related to ventricular arrhythmias than LVH. Antihypertensive drugs that can reduce LVH also have a beneficial effect on cardiovascular morbility and mortality.

Sudden death in heart failure

INTRODUCTIONnOur study was designed with the primary objective of evaluating the cardiac, overall and sudden mortality in patients with class IV heart failure (NYHA) managed with standard treatment and captopril (50 mg/8 hr. max.).nnnMATERIAL AND METHODSn95 consecutive patients were enrolled in 21 hospitals and were followed for 6 months in order to design an interventional clinical trial to reduce sudden death.nnnRESULTSnDeath occurred in 14 patients (14.7%; i.c. 8.3% - 23.5%; p < 0.05). There were no non-cardiovascular deaths in the group. There were 6 sudden death cases (42.9%; i.c. 16.9% - 68.8%, p < 0.05). Patients who died had a higher baseline end-diastolic (p < 0.05) and end-systolic (p < 0.01) diameter of the left ventricle (LV) and lower values of systolic (p < 0.01) and diastolic (p < 0.05) blood pressure. During the follow-up phase, heart rate, ventricular premature contraction, blood pressure and LV diameters decreased significantly in the whole group (p < 0.05, p < 0.001). We found no any differences during the follow-up phase between the patients who died and those who survived. In the patients who died we found no any differences between sudden death cases and the other death cases.nnnCONCLUSIONSnSudden death was less frequent than we had expected and due to this fact it is impossible for us to design an interventional trial.

3-dimensional Poincare plots of the QT intervals-an approach to nonlinear QT analysis

The Poincare plots-a simple graphical, nonlinear method was implemented to express 24-h QT interval changes. The group of 23 pts with hypertrophic cardiomyopathy was analyzed (11 pts. with higher and 12 with lower risk of sudden cardiac death). The control group consisted of 10 healthy subjects. 24-h Holter ECG recordings were analyzed and RR and QT intervals were measured beat by beat. 3 dimensional QT and RR plots were constructed in the time delay coordinates. Three main forms of QT plots were observed, highly different in cases with hypertrophic cardiomyopathy compared to normals. Different shapes of QT and RR plots revealed a complex nonlinear relation of the QT and RR intervals.

Autonomic function evaluated by entropy measures of the heart rate variability

Measurements of the system complexity analysis have been applied based on the Renyi and Shannon entropies, in order to describe the Heart Rate Variability (HRV). The RR series were obtained from ECG recordings of 117 subjects: Group IDC, containing 53 patients with idiopathic dilated cardiomyopathy; Group NRM, formed by 64 healthy people. Only the night period (O:OO-5:00 h) was considered for time-series analysis. The entropies were calculated in four spectral bands: very low frequency VLF (0-0.04 Hz), low frequency LF (0.04-0.15 Hz), high frequency HF (O.15-0.45 Hz) and in the total band TF (0-0.45 Hz). A study of the lags involved in the calculation of the entropies was carried out. All entropies showed significant statistical differences (p<0.001) comparing IDC and NRM groups, independently of the lag, except those obtained in the VLF band. A linear combination of the entropies, calculated in the HF, LF and VLF bands, permitted the IDC and NRM groups to be characterised.

A16-5 Automatic measurement of corrected qt interval in holter ECG as a marker of life-threatening arrhythmias in postmyocardial infarction patients

11.112 (1.62%) 823 (0.06%) 500msec compared to PMIP without MVA. Automatic measurement of QTc interval from Halter ECGs is now available and feasible and may be a marker for risk assessment of life-threatening arrhythmias, but further studies are needed to coniirm these results and to determine the predictive value. I

Sympatho-vagal activity described by the complex and deterministic behavior of heart rate variability

Presents new variables to improve the characterization of autonomic nervous system function by analyzing heart rate variability. These new variables are the effective energies (Efe), defined from the Hartley-Shannon theorem, in the three frequency bands Efe/sub VLF/ (0-0.04 Hz), Efe/sub LF/ (0.04-0.15 Hz) and Efe/sub HF/ (0.15-0.45 Hz). The effective energy is obtained using a complexity measure of the R-R signal (the Shannon entropy) and the instantaneous frequency, defined from the time-frequency representation. Two groups of subjects have been studied: 53 patients with idiopathic dilated cardiomyopathy (IDC) and 64 healthy people considered as the control group. The effective energies obtained in the VLF, LF and HF bands presented statistically significant differences (p<0.005) characterizing IDC patients. The instantaneous frequency contained in the VLF band was lower in IDC patients than in the control group. The main complexity differences given by the analyzed entropies were obtained in the LF and HF bands.

Markers and Triggers of Sudden Death in Athletes

The markers and triggers of sudden death in the general population have been well studied (1–3). In principle, they are related to the presence of a vulnerable myocardium in which some triggers or modulators may induce sudden death, generally through ventricular fibrillation (VF) (Fig. 1). Ventricular fibrillation may be triggered by a single event, as happens with a sustained ventricular tachycardia during a waterfall (Fig. 2) or by a more complex cascade of events (Fig. 3). Sometimes the final step is a bradyarrhythmia. This is relatively frequent in patients with advanced congestive heart failure (4) hut is rare in the ambulatory sudden death of patients with different types of heart disease (5) and in the acute phase of myocardial infarction (6) (Fig. 4).

Clinical Usefulness of QT Prolongation, QT Dispersion and T-Wave Alternans

The prognosis of postmyocardial infarction patients depends especially upon the interaction between ischemia, left ventricular dysfunction and electrical instability. Repolarization parameters (QT interval, QT dispersion and T-wave alternans analysis) are used for noninvasive evaluation of patients prone to ventricular arrhythmias after myocardial infarction. The publication of the results of the MADIT trial makes the development of new techniques for noninvasive risk stratification of arrhythmias even more important, because one of the major limitations to extrapolation of the results in daily clinical practice is the need for an invasive electrophysiological (EP) test to stratify the patients.

QT Dispersion: Its Clinical Value

Animal studies1–3 have shown that increased basic dispersion of repolarisation lowers the ventricular fibrillation threshold and facilitates induction of reentrant ventricular arrhythmias.