Baroreflex sensitivity as a new marker for risk stratification

As the arterial baroreflex importantly contributes to modulation of the aut onomic influences on the heart and thereby arrhythmogenesis, baroreflex sen sitivity has been used as a measure of the interaction between sympathetic and parasympathetic activities at the cardiac level. The most widely applie d technique both in the experimental and clinical setting is the measuremen t of the heart rate slowing in response to a blood pressure rise induced by small intravenous boluses of phenylephrine. Baroreflex sensitivity is expr essed as ms/mmHg and prevailing vagal reflexes are reflected by the wider R -R interval lengthening. The experimental evidence that the occurrence of V entricular fibrillation was inversely related to baroreflex sensitivity, op ened the way to clinical studies. The ATRAMI (Autonomic Tone and Reflexes A fter Myocardial Infarction) trial has definitely demonstrated not only that a depressed baroreflex sensitivity (< 3 ms/mmHg) is a strong risk factor f or cardiac death, but also that the information gained by the analysis of a utonomic markers adds to the information obtained by better recognized meas ures of cardiovascular outcome such as left ventricular function and ventri cular arrhythmias. The value of a depressed baroreflex sensitivity as a ris k stratifier is meaningful in patients below age 65 in combination of a sim ultaneously depressed left ventricular ejection fraction. In these patients , the analysis of autonomic activity might be of value in the identificatio n of patients who may need an implantable automatic defibrillator for prima ry prevention of sudden cardiac death.