Abstract

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 (pV̇o₂), steeper slope of minute ventilation (V̇e) to carbon dioxide production, lower exercise time and shorter 6 min walk test than PSF patients and controls. PSF_DD patients had lower pV̇o₂, 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 V̇e to symptoms (Borg/V̇e 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 V̇e. 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 V̇e than C_DD and patients with SHF.