[Sudden death (III). The causes of sudden death. Problems at the time of establishing and classifying the types of death]. / Muerte súbita (III). Causas de muerte súbita. Problemas a la hora de establecer y clasificar los tipos de muerte.

Sudden cardiac death is one of the main causes of death in Western countries. Identification of possible causes and their intrinsic mechanisms, is directed to achieve a better risk stratification, which permits the obtention of a more effective primary and secondary prevention. In the last two decades, important advances in the field of arrhythmia treatment have been obtained, which could have an important impact on the incidence of sudden death in the highest risk groups. However, the low positive predictive value of the diagnostic tools available nowadays, as well as the high number of patients who have sudden death as the first initial symptom of their disease, represent an important limitation for the primary prevention on the whole of the general population. In this article we review different diseases associated with sudden death, with special focus on the subgroup of patients with higher risk within each disease group, as well as the problems in establishing an accurate definition of sudden death.

[Image of pseudocapture caused by micro-dislodgment of the electrode in a VDD pacemaker]. / Imagen de seudocaptura por microdesplazamiento del electrodo en un marcapasos VDD.

The new AV sequential pacemakers have improved the suitability for the election of the best pacing mode for each patient. The complexity of the systems may mask some dysfunctions. In the presented case, a failure to capture due to micro-dislodgment, may have been missed in a simple pacemaker control, because of the combination of several factors: the presence of normal AV conduction at that moment, the concordance between the pacemaker stimulus and the conducted QRS complex and the similar morphology of the conducted and paced QRS complex.

Ventricular arrhythmias in left ventricular hypertrophy and heart failure.

The significance of ventricular hypertrophy in the genesis of ventricular tachyarrhythmias cannot be over-emphasized. Left ventricular hypertrophy, as a consequence of arterial hypertension, influences the three factors involved in the prognosis and we express these as a triangle of risk: electrical instability, left ventricular dysfunction and ischaemia.

Do silent myocardial ischemia and ventricular arrhythmias interact to result in sudden death?

The relationship between silent myocardial ischemia and sudden death depends on the severity and duration of the ischemia. Severe, transmural and persistent ischemia, as occurs in myocardial infarction, can trigger sudden death. When the ischemia is severe and transmural but not long-standing (e.g., Prinzmetal angina), ventricular arrhythmias appear frequently, but they are rarely malignant. In cases of subendocardial ischemia, there is no definitive proof of this relationship.