Right Atrial Pacing Research Articles

Atrial Pacing During Percutaneous Transluminal Coronary Angioplasty: Results and Comparison with Exercise Treadmill Testing

Right atrial pacing (RAP) was used to immediately assess improvement in threshold for myocardial ischemia in 23 patients undergoing angiographically successful percutaneous transluminal coronary angioplasty (PTCA). Multiple coronary lesions were present in 19 patients, and 15 had incomplete revascularization. All patients had RAP done immediately before and after completion of all dilatations, and in 13 patients pre- and post-PTCA exercise treadmill tests (ETT) were also performed. Angina occurred in 16 (70%) patients during pre-PTCA RAP, but in only 4 (17%) after PTCA (p less than .05). The electrocardiogram was positive for ischemia (horizontal or downsloping ST depression greater than or equal to 1 mm) in 18 patients (78%) during pre-PTCA RAP. However, 13 patients (57%) continued to have an ischemic response during post-PTCA RAP (not significant-NS). In 4 patients with multiple coronary lesions who had sequential pacing studies after PTCA of each lesion, the maximum degree of ST depression decreased by 1 mm or more after each dilatation in 3 patients but remained greater than or equal to 1 mm in all. In the 13 patients undergoing both RAP and ETT, angina developed in 7 during pre-PTCA RAP and in 2 after PTCA (p less than .05), compared with 8 and 3 (p less than .05) during pre- and post-PTCA ETT, respectively. Ischemic ST depression occurred in 9 patients during pre-PTCA RAP and in 6 after PTCA (NS), and in 8 and 6 (NS) during pre- and post-PTCA ETT, respectively. Concordance between the two tests was good.(ABSTRACT TRUNCATED AT 250 WORDS)

Early right atrial pacing after myocardial infarction: I. Comparison with early treadmill testing

Right atrial (RA) pacing and modified treadmill testing (TT) were performed in 111 patients recovering from acute myocardial infarction (MI) before hospital discharge to determine whether ischemic responses are more common with RA pacing than with TT and whether the prognosis could be better determined by the results of 1 test compared with the other. Patients with predischarge congestive heart failure, chest pain, physical disability or age older than 70 years were excluded. Ischemic responses were significantly more frequent during RA pacing than during TT (41% vs 34%, p = 0.02). The results of the 2 tests were concordant in 102 patients (92%): Both were positive in 37 and both negative in 65. In 8 patients, results of RA pacing were positive and results of TT were negative; only 1 patient had positive TT and negative RA pacing responses. The higher percentage of positive responses during RA pacing than during TT can be attributed to the significantly higher pressure-rate product achieved during pacing (18,773 vs 16,831 mm Hg/min, p < 0.001). The ischemic threshold, defined as the pressure-rate product at which an ischemic change was first noted in a particular patient, was almost identical in both tests. During a mean follow-up period of 16 months, 10 patients had recurrent MI; 8 had positive predischarge RA pacing but only 5 had positive TT responses (p = 0.008). Six patients died; in 3 RA pacing responses were positive and in 2 TT responses were positive. The predictive value of a positive RA pacing response for a subsequent major cardiac event (reinfarction or death) was 20% and that of a positive TT was 13% (p < 0.05). We believe that in patients who, at discharge, achieve a low pressure-rate product on the treadmill, RA pacing can provide important prognostic information. However, in postinfarction patients who achieve a high pressure-rate product on the treadmill, the results of this test are similar to the results of RA pacing and, therefore, the performance of 1 of the tests is sufficient.

Early right atrial pacing after myocardial infarction: II. Results in 77 patients with predischarge angina pectoris, congestive heart failure, or age older than 70 years

Seventy-seven consecutive postinfarction patients who had either predischarge angina pectoris or congestive heart failure, or who were older than 70 years of age, underwent right atrial (RA) pacing before hospital discharge. In 60% of these patients, ischemic changes developed during RA pacing; this high yield of positive response indicates advanced coronary arterial disease. During a mean follow-up of 15 months, these patients had a high mortality rate (18%) and a reinfarction rate of 9%. RA pacing separated this a priori high-risk group into lower- and higher-risk subsets. Of the 46 patients with a positive RA pacing response, 6 had reinfarction, while none of the 31 patients with a negative RA pacing response had reinfarction (p = 0.04); 10 of the 14 cardiac deaths were among the patients who had positive RA pacing responses at discharge (p = not significant). Thus, of the 20 major cardiac events, 16 occurred among those with positive RA pacing responses (p < 0.05). Predischarge clinical symptoms, however, were not good predictors of subsequent major cardiac events. We conclude that RA pacing can be safely performed even in high-risk and elderly patients and a positive response can identify those who have a poorer prognosis. Therefore, for postinfarction patients who, according to the prevailing criteria, are excluded from treadmill testing, we advocate the use of RA pacing.

Abolition of ischemic response to atrial pacing following aortocoronary bypass surgery.

To determine the effect of successful aortocoronary bypass surgery (ACBS) on left ventricular (LV) function, the ischemic response to right atrial pacing (RAP) was studied in 22 angina patients before and 3.8 +/- 1.1 months after surgery. All patients were free of angina after ACBS and had at least one patent graft. Before ACBS, RAP induced angina in 15 patients (Group 1) but not in 7 patients (Group 2). After ACBS, no patient had angina with RAP despite the increased maximum rate of pacing. Post-pacing LV end-diastolic pressure (LVEDP) after ACBS decreased in Group 1 from 25 +/- 6 to 15 +/- 6 mm Hg (P less than 0.01), but not in Group 2. Changes in ejection fraction, cardiac output, resting LVEDP, or LVEDP after LV angiography were not significant in either group and were therefore not useful in evaluating the result of ACBS. However the ischemic response to right atrial pacing was abolished by successful aortocoronary bypass surgery, suggesting improved myocardial perfusion during stress.

The effects of right atrial and ventricular pacing on the auscultatory findings in patients with mitral valve prolapse.

Fifteen patients with midsystolic clicks associated with mitral valve prolapse were studied in order to assess changed in ausculatatory findings produced by pacing-induced variations in cardiac rate, rhythm, and conduction. As the heart rate was increased in stepwise intervals to the maximum possible extent by right atrial pacing (RAP) in 14 patients, the interval between the Q wave and the click (Q-C) decreased in all cases (21 plus or minus msec/10 beats/min; P smaller than 0.001). In two patients, RAP at rates of and above 118 and 159 per minute, respectively, resulted in disappearance of the click. During right ventricular pacing (RVP) without evidence of atrioventricular (A-V) dissociation on the surface ECG in ten patients, the click was inaudible at all pacing rates in three instances. In all seven of the cases in which the click was audible at the lowest rate of RVP with VA conduction, Q-C was greater and C-S2 less than that in sinus rhythm. As the rate of RVP was increased, Q-C was noted to decrease (26 plus or minus 4 msec/10 beats/min) and C-S2 to increase (19 plus or minus 7 msec/10 beats/min) in all patients. In three patients in whom RVP induced atrioventricular dissociation, the click was seen only in beats closely preceded by a P wave. In ten of 11 patients the click occurred earlier in systole with a postextrasystolic or post tachycardia beat as compared to its appearance after a sinus beat when a shorter preceding diastolic filling period was present (P smaller than 0.001). In the eleventh patient a loud systolic murmur was present during a postextrasystolic cycles. It is concluded that pacing-induced rhythm disturbances can result in disappearance of a midsystolic click or can alter its timing and cause it to mimic sonic phenomena seen in other disease states. The possibility of similar changes taking place as a result of spontaneously occurring disturbances of rate, rhythm, and conduction should be recognized in order that the possible diagnosis of mitral valve prolapse not be overlooked.

Effects of cardiac arrhythmias on aortocoronary bypass graft blood flow velocity in man

Effects of cardiac arrhythmias on aortocoronary bypass graft blood flow velocity in man