Evidence of temporary sinus node dysfunction was found in two patients. One with inferolateral infarction had critical stenosis of the left circumflex artery with the SNA arising from its posterior portion. The other patient, with a subendocardial infarction, had severe three vessel disease, and a posterior SNA arising distal to the severe stenosis. Sinus bradycardia (<55 beats/min) during the first six hours of myocardial infarction was noted in nine patients, seven with inferior and two with inferolateral infarction, but the SNA was not involved in the infarction process. Nearly all patients had supraventricular or ventricular extrasystoles in the first 24 to 36 hours of infarction, although all received prophylactic lignocaine. buy zoloft online
The sinus node arteries in 307 of the 309 patients were angiographically atheroma free. Two hundred sixty-one of our 309 patients had a right dominant coronary arterial system (posterior descending artery originating from the right coronary artery), 45 had a left dominant coronary arterial system (posterior descending artery originating from the left circumflex), and three had a balanced type with two posterior descending arteries, one arising from the right coronary artery and one from the left circumflex.

The sinus node artery originated from the right coronary artery in 182 patients (59 percent), the left circumflex in 119 patients (38 percent), and both coronary arteries in eight patients (3 percent). Of the sinus node arteries arising from the right coronary artery, the right sinus node arteries, the majority (179) arose proximally 1 to 3 cm from the aortic ostium, passed across the anteromedial wall of the right atrium, and penetrated the atrial septum below the interatrial bundle (Fig 1). Two variations in the origin and course of the right sinus node artery were observed in three patients. In one the sinus node artery originated near the origin of the acute marginal artery and then coursed upward over the lateral wall of the right atrium to the sinus node (Fig 2). This was one of the two sinus node arteries that showed atheroma. In two others the sinus node artery arose to the left of the crux. It ran over the superior aspect of the left atrium and then looped inferiorly into the interatrial septum before its passage superiorly to reach the sinus node (Fig 3).
In 87 of the 119 patients in whom the sinus node artery arose from the left circumflex coronary artery, it arose from the proximal portion of the left circumflex and coursed through the anterior ramus of the interatrial muscle bundle and then through the bundle itself (Fig 4). In the remaining 32 patients the sinus node coronary artery arose from the left circumflex artery below its origin at any point throughout its length, curved gently upward and backward in the region of the left atrium between the atrial appendage and the left superior pulmonary vein, and reached the atrial septum. From there it ran to the base of the superior vena cava, which it encircled before penetrating the center of the sinus node. Of the 32 arteries following this course, which are named the “posterior sinus node arteries,” ten originated from the upper part of a divided left: circumflex (Fig 5), 16 constituted a branch of the left circumflex (Fig 6), and six formed the main continuation of this artery (Fig 7). In each case the same basic route to the sinus node area was followed. Finally, in eight patients there were two sinus node coronary arteries, one arising from the right coronary artery and one from the left circumflex artery.

Figure 1. Right coronary arteriogram in right anterior oblique projection showing origin of sinus node artery (arrow) at beginning of right coronary artery.

Figure 1. Right coronary arteriogram in right anterior oblique projection showing origin of sinus node artery (arrow) at beginning of right coronary artery.

Figure 2. Right coronary arteriogram in right anterior oblique projection showing sinus node artery (arrow) originating near origin of acute marginal artery.

Figure 2. Right coronary arteriogram in right anterior oblique projection showing sinus node artery (arrow) originating near origin of acute marginal artery.

Figure 3. Right coronary arteriogram in left anterior oblique projection showing origin and course of sinus node artery (arrow) arising left of crux.

Figure 3. Right coronary arteriogram in left anterior oblique projection showing origin and course of sinus node artery (arrow) arising left of crux.

Figure 4. Left coronary arteriogram in right anterior oblique projection. Sinus node artery (arrow) arises from proximal portion of left circumflex artery and courses along body of left atrium to sinoatrial node.

Figure 4. Left coronary arteriogram in right anterior oblique projection. Sinus node artery (arrow) arises from proximal portion of left circumflex artery and courses along body of left atrium to sinoatrial node.

Figure 5. Left coronary arteriogram in left lateral projection. “Posterior sinus node artery” originates from upper part of divided left circumflex artery (arrow).

Figure 5. Left coronary arteriogram in left lateral projection. “Posterior sinus node artery” originates from upper part of divided left circumflex artery (arrow).

Figure 6. Left coronary arteriogram in right anterior oblique projection. “Posterior sinus node artery” (arrow) constitutes a branch of left circumflex artery.

Figure 6. Left coronary arteriogram in right anterior oblique projection. “Posterior sinus node artery” (arrow) constitutes a branch of left circumflex artery.

Figure 7. Left coronary arteriogram in left anterior oblique projection. “Posterior sinus node artery” (arrows) constitutes main continuation of left circumflex artery.

Figure 7. Left coronary arteriogram in left anterior oblique projection. “Posterior sinus node artery” (arrows) constitutes main continuation of left circumflex artery.