The clinical, electrocardiographic and electrophysiologic determinants and effects of antiarrhythmic agents on sustained
sinus node reentrant tachycardia remain poorly defined. Of 65 consecutive men undergoing electrophysiologic studies for symptomatic
paroxysmal supraventricular tachycardia over a 4 year period, 11 (16.9%), who ranged in age from 39 to 76 years, demonstrated sustained
sinus node reentrant tachycardia. On the surface electrocardiogram, before electrophysiologic studies, the following diagnoses were considered in the 11 patients:
sinus node reentrant tachycardia on the basis of an RP'/P'R ratio of greater than 1 and P wave configuration similar to that of sinus P waves (7 patients); atrioventricular (
AV) nodal reentrant tachycardia on the basis of an RP'/P'R ratio of less than 1 (3 patients); and paroxysmal atrial
tachycardia with
AV block (1 patient). All 11 patients had a history of recurrent palpitation, 4 had
syncope, 2 had dizzy spells and 9 had organic
heart disease. Sustained
sinus node reentrant tachycardia could be reproducibly induced in all 11 patients during atrial pacing or premature atrial stimulation, or both, over a wide echo zone. The
tachycardia could be terminated by carotid sinus
massage, atrial pacing and premature atrial stimulation. Characteristics of
tachycardia included: high-low activation sequence; cycle lengths of 250 to 590 ms with wide fluctuations of 20 to 180 ms in individual patients; RP'/P'R ratio of greater than 1 in 8 (73%) of the 11 patients and a ratio of less than 1 in 3 (27%). Induction of sustained
sinus node reentrant tachycardia was prevented by intravenous
ouabain (0.01 mg/kg
body weight) in two of two patients, by intravenous
verapamil (10 mg) in two of two patients and by intravenous
amiodarone (5 mg/kg
body weight) in four of four patients. In contrast, intravenous
propranolol (0.1 mg/kg
body weight) did not affect induction of sustained
sinus node reentrant tachycardia in two of two patients. It is concluded that sustained
sinus node reentrant tachycardia, seen in 16.9% of the study patients with
paroxysmal supraventricular tachycardia, is not as benign as previously believed; it is frequently associated with organic
heart disease; it demonstrates wide variations in cycle length, unlike other forms of
paroxysmal supraventricular tachycardia; it can masquerade as
AV nodal reentrant tachycardia and paroxysmal atrial
tachycardia with
AV block on the surface electrocardiogram in 36% of patients; and it is responsive to
intravenous administration of
ouabain,
verapamil or
amiodarone.