Critical Level of Cerebral Oxygenation During Exercise in Patients With Left Ventricular Dysfunction

Background In a recent study the indexes of cerebral oxygenation decreased during maximal exercise in nearly half of all patients with left ventricular dysfunction. Whether these levels decrease severely enough to influence mental status or level of consciousness was evaluated in the present study. Methods and Results Forty-two patients with idiopathic dilated cardiomyopathy (IDC) and 29 healthy subjects underwent a symptom-limited maximal exercise test. The cerebral oxyhemoglobin (O2Hb) and tissue oxygenation index (TOI) were continuously monitored using near-infrared spectroscopy. The changes in O2Hb and TOI were also measured in 7 subjects: 2 who experienced episodes of reduced consciousness caused by sudden decreases in blood pressure during exercise recovery and 5 who exhibited sustained ventricular tachycardia during an electrophysiological study. The change in cerebral O2Hb during exercise in patients with IDC averaged 0.38±3.39 μmol/L, significantly lower than in the normal subjects (4.30±4.47 μmol/L, p