Electrophysiologic studies with recordings of sinus node electrograms were performed in 38 @entity1 with severe symptomatic @entity1817 . Thirty-two of the 38 @entity1 had @entity591 and 17 presented with @entity1163 . The clinically documented sinus or atrial pause was 5.6 +/- 2.8 s (mean +/- SD). @entity1 were divided into three groups according to electrophysiologic findings. Group I consisted of nine @entity1 with complete @entity9765 . Sinus node electrograms were recorded during the episodes of long pauses. Seven @entity1 had unidirectional exit block, with the atrial impulse being capable of retrograde penetration to the sinus node causing suppression of sinus automaticity; two had bidirectional @entity9765 . Group II consisted of 22 @entity1 with either 1:1 sinoatrial conduction (group IIa = 13 @entity1 ) or second degree @entity9765 (group IIb = 9 @entity1 ) during spontaneous sinus rhythm. @entity9765 , ranging from 1 to greater than 14 sinus beats, was observed during postpacing pauses that ranged from 1,650 to 37,000 ms (mean 7,286 +/- 6,989). The maximal sinus node recovery time ranged from 770 to 5,580 ms (mean 3,004 +/- 1,686) and was normal in 5 @entity1 and prolonged in 17. Group III consisted of seven @entity1 with no recordable sinus node electrogram, reflecting either a technical failure or a quiescence of sinus activity. The sinus node recovery time in these seven @entity1 ranged from 1,190 to 4,260 ms (mean 2,949 +/- 1,121). Thus, @entity1817 and sinoatrial conduction are responsible for the long sinus or @entity1817 . However, complete @entity9765 can occur and cause severe @entity1168 with escape rhythm; repetitive @entity9765 plays a major role in producing posttachycardia pauses.

Sinus automaticity and sinoatrial conduction in severe symptomatic XXXX .

@entity1 :: ('9606', 'Species') :: ['Patients', 'patients'] @entity9765 :: ('MESH:D012848', 'Disease') :: ['sinoatrial exit block', 'sinoatrial block', 'Sinoatrial exit block'] @entity1163 :: ('MESH:D013575', 'Disease') :: ['syncope'] @entity591 :: ('MESH:D013610', 'Disease') :: ['episodic tachyarrhythmias'] @entity1817 :: ('MESH:D012804', 'Disease') :: ['sick sinus syndrome', 'abnormalities in both sinus node automaticity', 'atrial pauses in the sick sinus syndrome'] @entity1168 :: ('MESH:D001919', 'Disease') :: ['bradycardia']
@entity1817 :: (MESH:D012804,Disease) :: ['sick sinus syndrome']
