Impacto de la angioplastia primaria en la indicación de desfibrilador implantable en pacientes con infarto de miocardio

Heart rate turbulence denoising using support vector machines

Heart rate turbulence (HRT) is a transient acceleration and subsequent deceleration of the heart rate after a premature ventricular complex (PVC), and it has been shown to be a strong risk stratification criterion in patients with cardiac disease. In order to reduce the noise level of the HRT signal, conventional measurements of HRT use a patient-averaged template of post-PVC tachogram (PPT), hence providing with long-term HRT indexes. We hypothesize that the reduction of the noise level at each isolated PPT, using signal processing techniques, will allow us to estimate short-term HRT indexes. Accordingly, its application could be extended to patients with reduced number of available PPT. In this paper, several HRT denoising procedures are proposed and tested, with special attention to support vector machine (SVM) estimation, as this is a robust algorithm that allows us to deal with few available time samples in the PPT. Pacing-stimulated HRT during electrophysiological study are used as a low-noise gold standard. Measurements in a 24-h Holter patient database reveal a significant reduction in the bias and the variance of HRT measurements. We conclude that SVM denoising yields short-term HRT measurements and improves the signal-to-noise level of long-term HRT measurements.

[Primary prophylaxis with the implantable cardioverter-defibrillator in heart failure: a clinical point of view]

The implantable cardioverter-defibrillator (ICD) is one of the great inventions of modern cardiology. Its use for the prevention of sudden death in patients with left ventricular dysfunction has meant that clinical cardiologists are now fully involved in decision-making on the implantation of these devices. The majority of clinical trials, which have used low ejection fraction as the only or main criterion for patient recruitment, have shown that ICD use leads to a significant improvement in survival. Three trials, two of which were carried out soon after myocardial infarction and one of which was performed at the same time as surgical revascularization, were exceptions. However, it is important to be aware that the improvements observed in the most recent trials have not been as large as those seen in the initial studies. Reduced efficacy has meant that in the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), for instance, 25 ICDs had to be implanted to save one life over a 2-year period. The most likely explanation for this observation is that the better prognosis achieved by present-day pharmacologic treatment of heart failure has reduced the margin of benefit associated with ICD use. Another consequence is that depressed left ventricular ejection fraction has lost some of its specificity in predicting sudden death. New predictive variables are needed to improve risk stratification in this population. Without these variables, the use of ICDs in the primary prevention of sudden death in patients with left ventricular dysfunction will not seem a very attractive option from the point of view of good clinical practice.