Objectives: To establish the prevalence of preserved left ventricular (LV) systolic function (PSF) in 435 consecutive symptomatic patients referred to a heart failure clinic and to examine their ventilatory response to exercise when compared with 134 control volunteers.
Methods: 216 (50%) patients had systolic heart failure (SHF) (ejection fraction < 45%). 51 (11%) had an immediately apparent alternative causes of breathlessness and 168 (39%), with no obvious other cause of breathlessness, were divided into those with PSF and diastolic dysfunction (DD) (PSF(DD); n = 113 or 26% of referrals) and those without DD (PSF(N); n = 55 or 13% of referrals). The controls were divided into those with (C(DD); n = 32) and those without (C(N); n = 102) echocardiographic evidence of DD.
Results: Patients with SHF had lower peak oxygen consumption (pVo(2)), steeper slope of minute ventilation (Ve) to carbon dioxide production, lower exercise time and shorter 6 min walk test than PSF patients and controls. PSF(DD) patients had lower pVo(2), exercise time and 6 min walk test than C(DD), although their echocardiograms were not different. Exercise capacity did not differ between PSF(DD) and PSF(N) patients. The slope relating Ve to symptoms (Borg/Ve slope) was less steep in those with SHF than in PSF(DD) (0.17 (0.04) v 0.20 (0.08), p < 0.05) and in PSF(N) (0.19 (0.10), p < 0.05), implying greater symptoms of breathlessness for a given level of Ve. Both PSF groups had a steeper slope than C(DD) (0.14 (0.09), p < 0.05 for both comparisons).
Conclusions: Patients with PSF have exercise tolerance intermediate between that of patients with SHF and controls. Exercise tolerance is similar in PSF(DD) and PSF(N). Both groups have worse exercise tolerance than C(DD). PSF(DD) and PSF(N) patients seem to experience a greater awareness of Ve than C(DD) and patients with SHF.