Aerobic Capacity in Rate Modulated Pacing

Whether heart rate or AV synchrony is the most important factor for an increase in aerobic capacity was evaluated in a comparative study between sinus bradycardia, VVIR, DDD, and DDDR stimulation. Sixteen patients (mean age 67 years) with chronotropic incompetence and impJanted DDDR pacemaker (Telectronics META 1250) were randomly studied by cardiopulmonary exercise testing. All patients were exercised to their anaerobic threshold (ATJ with the following heart rates: DDD 84 ± 3, WIR 110 ± 5, and DDDR 116 ± 6 beats/min. Mean oxygen uptake (VO₂, mL/kg per min) at AT was 7.4 ± 0.3 in DDD and WIR modes. A 12% increase was measured in DDDR mode (8.3 ± 0.4). Compared to VVIR work capacity in the DDDR mode was improved by 17% (41 vs 48 W/min). In patients with isolated sinus node disease (n = 9) the increase of VO₂ and work capacity at AT during DDDR mode was more pronounced (16% and 20%, respectively, compared to VVIR). In patients with intermittent second or third degree AV block (n = 7) the differences between the pacing modes were not significant. This might partly be due to a lesser degree of chronotropic incompetence in this subgroup. In conclusion only the conjunction of heart rate increase and preservation of AV synchrony provides a significant improvement in aerobic capacity during exercise.     

Coronary Artery Stenting in Vessels with Reference Diameter < 3 MM

The study included 220 consecutive patients with coronary artery stenting. In 128 patients (60.8 ± 10.2 years, 68% men), a total of 184 stents were placed in coronary vessels with a reference diameter < 3 mm (group S). One hundred thirty-four stents were implanted in 92 patients (62.9 ± 9.8 years, 82.6% men) in vessels > 3 mm (group L). There was no significant difference according to clinical baseline characteristics. The primary end point of this retrospective study was the rate of periinterventional complications (death, stent thrombosis, myocardial infarction, urgent angioplasty, or surgical revascularization). The, secondary end point was the clinical and angiographic follow-ups (restenosis, recurrent angina, further revascularization) after 3 months. Cardiac complications occurred in group S in two (1.6%) patients, two stent thromboses with urgent angioplasty, one Q-wave and one non-Q-wave infarction. There was one (1.1%) event in group L, a stent thrombosis with Q-wave infarction and urgent angioplasty. Angiography at 3-month follow-up was performed in 148 patients. Restenosis occurred in group S in 31.8% and in group L in 21.7% (NS). Data according recurrent angina and recommended surgical revascularization did not differ between both groups. In group S, significantly more angioplasties of the stented lesion were performed (23/60 patients) compared to group L (6/88) (P = 0,015). Coronary artery stenting in vessels with a reference diameter < 3 mm can be performed without a high rate of periinterventional complications. Restenosis tends to be more frequent in the small vessel group, a higher rate of reangioplasties have to be expected. The clinical follow-up is comparable to a control group.