Effect of Nifedipine on the Sick Sinus Syndrome

Abstract

The effect of nifedipine (N) on sinus node (SN) function was studied in 15 patients (9 males, 6 females) sixty-two to seventy-six (mean 68.1 ±11) years old, with sick sinus syndrome (SSS). SSS was characterized electrophysiologically by a prolonged corrected sinus node recovery time (CSNRT > 535 msec) and/or prolonged sinoatrial conduction time (SACT > 125 msec), assessed by applying premature atrial stimulation. Ten mg N was given sublingually, and CSNRT and SACT were again evaluated sixty minutes after N administration, and again ten minutes after 1.5 mg atropine (A) was given IV. Heart rate increased significantly after N (p < 0.005), systolic blood pressure (SBP) diminished sig nificantly (p < 0.005), and CSNRT and SACT shortened significantly (p < 0.005, p < 0.005) and became normal in 7 and 5 patients respectively. After A administration, a further significant increase of heart rate (p < 0.005) and decrease of CSNRT (p < 0.005) and SACT (p < 0.005) were observed. CSNRT and SACT became normal in 8 and 7 patients respectively. SBP remained sta ble.