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Propranolol Decreases Tachycardia and Improves Symptoms in the Postural Tachycardia Syndrome (POTS)
Postural orthostatic tachycardia syndrome (often referred to as Postural Tachycardia Syndrome or POTS) is a condition of dysautonomia, and more specifically, orthostatic intolerance, in which a change from the supine position to an upright position causes an abnormally large increase in heart rate, called tachycardia. This is often, but not always, accompanied by a fall in blood pressure. Several studies show a decrease in cerebral blood flow with systolic and diastolic cerebral blood flow (CBF) velocity decreased 44 and 60%, respectively. Patients with POTS have problems maintaining homeostasis when changing position, i.e. moving from one chair to another or reaching above their heads. Many patients also experience symptoms when stationary or even while lying down. Symptoms present in various degrees of severity depending on the patient. POTS is a serious, though non-life threatening, medical condition that can be severely disabling and debilitating. Some patients are unable to attend school or work, and especially severe cases can completely incapacitate the patient. ?-Blockade is an appealing treatment approach, but conflicting preliminary reports are conflicting. As a result, a study published in Circulation (2009;120:725-734), was performed to test the hypothesis that propranolol will attenuate the tachycardia and improve symptom burden in patients with POTS. In study 1, patients with POTS (n=54) underwent acute drug trials of propranolol (20 mg) and placebo, on separate mornings, in a randomized crossover design. Blood pressure, heart rate, and symptoms were assessed while the patients were seated and after standing for up to 10 minutes before and hourly after the study drug. Supine (P<0.001) and standing (P<0.001) heart rates were significantly lower after propranolol compared with placebo. The symptom burden improvement from baseline to 2 hours was greater with propranolol than placebo (P=0.044). In study 2, 18 patients with POTS underwent similar trials of high-dose (80 mg) versus low-dose (20 mg) propranolol. Although the high dose elicited a greater decrease than the low dose in standing heart rate (P<0.001) and orthostatic tachycardia (P<0.001), the improvement in symptoms at 2 hours was greater with low-dose propranolol (P=0.041). According to the authors, low-dose oral propranolol significantly attenuated tachycardia and improved symptoms in POTS and that higher-dose propranolol did not further improve, and may worsen, symptoms.

Source: OnTarget Newsletter      21-9-2009