Figure 5.

Long term heart rate variability in a patient with a Medtronic implanted biventricular defibrillator (cardiac resynchronization device implanted in patients with severe cardiomyopathy and ventricular dyssynchrony). The device continuously records heart rate and heart rate variability data. In addition, thoracic impedance is measured, which correlates with the degree of pulmonary congestion and severity of heart failure symptoms. Sudden decrease in heart rate variability may be observed at the onset of increasing pulmonary congestion (decreased thoracic impedance due to fluid buildup). As these findings may precede the onset of symptoms by several days, remote monitoring may identify high risk patients for targeted intervention.