In 35 patients aged 18 to 69 years (mean 48) with clinical, electrocardiographic, or electrophysiological evidence of normal sinus node function, the effect of intravenous propranolol (0.1 mg/kg) was assessed on 3 indices of sinus node function. The drug significantly prolonged sinus node cycle length (12%), slightly prolonged the corrected sinus node recovery time (15%), and slightly but insig...

Endurance athletes exhibit sinus bradycardia, that is a slow resting heart rate, associated with a higher incidence of sinus node (pacemaker) disease and electronic pacemaker implantation. Here we show that training-induced bradycardia is not a consequence of changes in the activity of the autonomic nervous system but is caused by intrinsic electrophysiological changes in the sinus node. We dem...

The electrophysiologic effects of intravenously administered disopyramide (2 mg/kg) on three parameters of sinus node function were examined in 16 symptomatic patients with sinus node dysfunction. Based on their ECG data before study, patients were subdivided into group A (n = 8), those with sinus pauses and/or sinoatrial (SA) exit block; and group B (n = 8), those with sinus bradycardia. Disop...

The electrophysiologic effects of intravenously administered disopyramide (2 mg/kg) on three parameters of sinus node function were examined in 16 symptomatic patients with sinus node dysfunction. Based on their ECG data before study, patients were subdivided into group A (n = 8), those with sinus pauses and/or sinoatrial (SA) exit block; and group B (n = 8), those with sinus bradycardia. Disop...

Sinus node dysfunction is de~ned as inappropriate sinus bradycardia or abnormal pauses in sinus mechanism. Sinus node dysfunction often coexists with atrial ~brillation, _utter, or tachycardia, and in such cases may be termed “tachy-brady syndrome.” Sinus node dysfunction may also be accompanied by abnormalities of AV conduction. Another term for sinus node dysfunction is “sick sinus syndrome.”...

A transthoracic echocardiogram showed marked hypertrophy of the left ventricular apex (fig 1). There was no septal hypertrophy, systolic anterior motion of the mitral valve, or evidence of left ventricular outflow tract obstruction. A 24 hour ECG detected asymptomatic episodes of non-sustained ventricular tachycardia. On treadmill exercise testing he managed 10 minutes of the Bruce protocol wit...

A transthoracic echocardiogram showed marked hypertrophy of the left ventricular apex (fig 1). There was no septal hypertrophy, systolic anterior motion of the mitral valve, or evidence of left ventricular outflow tract obstruction. A 24 hour ECG detected asymptomatic episodes of non-sustained ventricular tachycardia. On treadmill exercise testing he managed 10 minutes of the Bruce protocol wit...

BACKGROUND Sinus node (SN) dysfunction is observed in some long-QT syndrome (LQTS) patients, but has not been studied as a function of LQTS genotype. LQTS6 involves mutations in the hERG β-subunit MiRP1, which also interacts with hyperpolarization-activated, cyclic nucleotide gated (HCN) channels-the molecular correlate of SN pacemaker current (If ). An LQTS registry search identified a 55-year...

BACKGROUND AND OBJECTIVES Cardiovascular changes associated with neuraxial blocks are a cause of concern due to their frequency and because some of them can be considered physiological effects triggered by the sympathetic nervous system blockade. The objective of this study was to evaluate intraoperative cardiovascular complications and predictive factors associated with neuraxial blocks in pat...