We studied the impact of a 6-wk supervised, multimodality endurance exercise training program (EXT) on strength and endurance of ventilatory and peripheral muscles in patients with chronic airflow limitation (CAL), and determined whether potential improvements contributed to relief of exertional breathlessness (B) and perceived leg effort/discomfort (LE), respectively. Twenty breathless patients with stable CAL (FEV1 = 41 +/- 3% predicted; mean +/- SEM) were tested at 6-wk intervals at baseline, after a nonintervention control period (pre-EXT), and post-EXT. Measurements included: pulmonary function tests (PFTs), maximal inspiratory/expiratory pressures (MIP, MEP), inspiratory muscle endurance (V(LIM)), quadriceps strength and endurance, exercise endurance, and submaximal cycle exercise with cardioventilatory and symptom responses. Measurements at baseline and pre-EXT were identical. Post-EXT, PFTs did not change; exercise endurance measured on the treadmill, cycle ergometer, arm ergometer, and by 6-min walk distance increased 40 +/- 8%, 43 +/- 10%, 12 +/- 5%, and 34 +/- 9%, respectively (p < 0.05); quadriceps strength increased 21 +/- 5% (p < 0.01); MIP and MEP increased 29 +/- 11% and 27 +/- 11%, respectively (p < 0.05); V(LIM) increased almost threefold (p < 0.05). At isotime near end-exercise, B, LE, carbon dioxide production (VCO2), oxygen consumption (VO2), ventilation, and breathing frequency (F) all fell after EXT (p < 0.05): deltaB correlated with deltaF (r = 0.58, p < 0.01). Increased MIP and V(LIM) did not correlate with improved breathlessness or exercise endurance. Similarly, changes in quadriceps strength and endurance did not correlate with changes in LE or exercise endurance. In conclusion, general nonspecific EXT improved ventilatory and peripheral muscle function in severe CAL, but such improvements did not appear to contribute significantly to reduced exertional symptoms and enhanced exercise performance.

Exercise in chronic airflow limitation (CAL) is often limited by symptoms before the physiologic boundaries of maximal ventilatory or cardiovascular capacities are attained. Symptom amelioration should translate directly into improved exercise performance. We studied the impact of a 6-wk supervised multimodality endurance exercise program (EXT) on perceived breathlessness (B) and leg effort (LE) and sought a physiologic rationale for symptom improvement. Thirty patients with CAL (FEV1/FVC = 42 +/- 2%, mean +/- SEM) were tested before and after EXT. Their responses were compared with those of a matched control group (n = 30; FEV1/FVC = 44 +/- 2%) after a nonintervention period. Testing included pulmonary function tests, chronic dyspnea evaluation (Baseline/Transition Dyspnea Index [BDI/TDI]), and graded cycle exercise with cardioventilatory monitoring and Borg scaling of B and LE. Spirometry did not change (delta) post-EXT. EXT significantly (p < 0.001) reduced chronic breathlessness (TDI = +2.8 +/- 0.3) compared with control (TDI = 0.0 +/- 0.3). Exertional symptoms of B and LE also fell (p < 0.01) after EXT (slopes of B and LE relative to VO2 fell by 14 and 23%, respectively; delta B/VO2 was associated with delta LE/VO2, r = 0.52, p < 0.01). Post-EXT slopes of B over ventilation (VE) also decreased by 10% (p < 0.025). Total cycle work increased 142 +/- 70% (p < 0.001) post-EXT and correlated primarily with delta B/VO2 (r = -0.64, p < 0.001). The best correlate of delta B/VO2 was delta VE/VO2 (r = 0.47, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Background-The INTRINSIC RV (Inhibition of Unnecessary RV Pacing with AVSH in ICDs) study tested the hypothesis that dual-chamber rate-responsive (DDDR) with atrioventricular search hysteresis (AVSH) 60-130 programming is not inferior to single-chamber (VVI)-40 programming in an implantable cardioverter defibrillator with respect to all-cause mortality and heart failure hospitalizations using an equivalence margin of 5%. Methods and Results-At 108 centers, 1530 patients with an implantable cardioverter defibrillator indication received a VITALITY AVT (Guidant Corporation, St. Paul, Minn) implantable cardioverter defibrillator programmed consistently to DDDR AVSH 60-130 for the first week. Of those, 988 patients with Ͻ20% right ventricular pacing at 1 week were randomized to DDDR AVSH 60-130 or to VVI-40 programming. Among those randomized, 502 were assigned to DDDR AVSH and 486 to VVI. Groups were similar with regard to coronary disease (68%), gender (21% female), and New York Heart Association functional class ϾI (79%). A total of 32 patients (6.4%) in the DDDR AVSH arm and 46 patients (9.5%) in the VVI arm died or were hospitalized for heart failure during a mean follow-up of 10.4 months (relative riskϭ0.67, Pϭ0.072 in favor of DDDR AVSH). DDDR AVSH was not inferior to VVI programming (PϽ0.001). All-cause mortality was not significantly different between the DDDR AVSH arm (3.6%) and the VVI arm

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