[Cardiovascular disorders during sleep]

Holter recordings of subjects apparently free from cardiovascular disease have demonstrated a moderate sinusal and nodal depression during sleep. This depression does not seem to be sufficient to create overt cardiovascular disorders in apparently healthy subjects, but it may aggravate or even reveal an underlying disorder of rhythm or conduction in elderly people or in patients taking drugs that potentiate its effects. In sleep apnea syndrome prolonged episodes of apnea may produce a paroxysmal, then permanent increase in pulmonary arterial pressure, which may lead to right heart failure. These episodes also increase the pre- and after-load and decrease myocardial contractility, thus facilitating the occurrence of left ventricular failure, potentiated by systemic arterial hypertension, overweight or even coronary disease, all conditions that are often present in these subjects. Arterial hypertension is so frequent in sleep apnea syndrome that some authors advocate a systematic search for the syndrome by Holter recordings before the hypertension is pronounced "essential". All studies confirm the existence of rhythm and conduction disorders directly related to apneic episodes. These disorders decrease or regress after a well-conducted treatment of the sleep apnea syndrome. They are mainly of the "hypokinetic" type, created by depression of sinus activity and conduction pathways. Their frequency, their severity and, in particular, the risk of sudden death they carry seem to have been overestimated, especially since no evidence has ever been produced of a potentially lethal rhythm disorder occurring during sleep apnea. Nevertheless, there is no certainty that these patients are not at risk of sudden death related to their sleep apnea syndrome.