Response of normal and abnormal sinus node to right ventricular stimulation.

Right ventricular pacing at progressively increasing rates was performed in 25 patients with complete ventriculoatrial block, before and after autonomic blockade with intravenous propranolol and atropine. At the end of each ventricular pacing stage a right intraatrial electrogram and electrocardiographic leads were simultaneously recorded. The relation between right ventricular pacing and atrial rates was studied from the recordings obtained at each pacing stage in both group I, 8 patients with sick sinus syndrome, and group II, 17 patients with normal sinus function. Right ventricular pacing was associated with an increment in atrial rate that ws significantly smaller (probability [p] less than 0.001) in patients in group I (mean +/- standard error of the mean 8 +/- 6 beats/min) than in group II (mean 25 +/- 10 beats/min). The maximal atrial rate reached during right ventricular pacing exceeded 80 beats/min in all patients in group II but remained less than 74 beats/min in patients in group I. Because autonomic blockade did not significantly influence the preceding results, it is concluded that a mechanical effect on the sinus node may explain this phenomenon.

[Acute posterior myocardial infarction involving the right ventricle. Anatomical study]. / Infarctus myocardique postérieur aigu : la participation ventriculaire droite. Etude anatomique.

Thirty patients who died in the acute phase of an inaugural posterior myocardial infarction were classified in two groups: group A, 14 cases, and group B, 16 cases without extension to the right ventricle. The autopsy examination showed the following differences. In group A: 1. The right coronary artery (RCA) gave off the posterior descending artery in all cases; 2. The RCA had diffuse atheromatous change in 10 cases (p less than 0,05); 3. Total occlusion of the RCA by thrombosis was constant (p less than 0,01) and was always proximal to or near the origin of the right marginal artery (p less than 0,001); 4. Postero-septal extension was constant and nearly always transmural (p less than 0,001).

[Recent myocardial infarction. Study of sinus function]. / Infarctus du myocarde récent. Etude de la fonction sinusale.

The ECGs of 70 consecutive patients hospitalised for a first transmural myocardial infarction (MI) (28 anterior, 42 posterior) were analysed prospectively and systematically during the acute phase. Endocavitary electrophysiological studies (EEP) were performed on the 21st day. The following conclusions were drawn: --Sinus bradycardia in the acute phase was observed in 18 cases (26 p. 100). Its cause is uncertain and its occurrence has no relation to the site of infarction. The single case of sinoatrial block (SAB) was recorded in a patient with a posterior MI. --EEP were normal in 18 patients who had sinus bradycardia during the acute phase; EEP was clearly pathological in the case with SAB. --There was no statistical difference in the incidence of pathological EEPs (p greater than 0,05) in anterior (4 out of 28 patients) and posterior (5 out of 42 patients) MI.