Excessive breathlessness in patients with 'diastolic heart failure'

Klaus K Witte ^1*, Nikolay P Nikitin ², John GF Cleland ² and Andrew L Clark ²

¹ Mount Sinai Hospital, Canada
² University of Hull, United Kingdom

^* To whom correspondence should be addressed. E-mail: klauswitte{at}hotmail.com.

Accepted 24 March 2006

Abstract

Background Approximately half of patients seen for the first time with heart failure have preserved left ventricular (LV) systolic function. Patients with heart failure due to systolic LV dysfunction have a reduced peak oxygen consumption (pVO2) and a steeper slope relating ventilation (VE) to carbon dioxide production (VCO2)(VE/VCO2 slope). The pattern of abnormalities on exercise of patients with diastolic heart failure is not well documented.

Aim To establish the frequency of preserved left ventricular function 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.

Results 216 (50%) patients had preserved LV systolic function (PSF) (EF>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) (PSFDD), (n=113 (26% of referrals)), and those without DD, (PSFN), (n=55 (13% of referrals)). The controls were divided into those with echocardiographic evidence of DD (CD) (n=32) and those without (CN(n=102). Patients with systolic heart failure (SHF) had lower pVO2, steeper VE/VCO2 slope, lower exercise time (ET) and shorter six-minute walk test (6MWT) than PSF patients and controls. PSFDD patients had lower pVO2, ET, and 6MWT than CDD although their echocardiograms were not different. There was no difference in exercise capacity between PSFDD and PSFN patients. The slope relating VE to symptoms (Borg/VE slope) was less steep in those with SHF than in PSFDD (0.17 (0.04) v 0.20 (0.08); p<0.05), and in those with PSFN (0.19 (0.10);p<0.05) implying greater symptoms of breathlessness for a given level of ventilation, and both preserved systolic function groups had a steeper slope than CDD, (0.14, (0.09);p<0.05 for both comparisons).

Conclusions Patients with PSF have exercise tolerance intermediate between patients with SHF and controls. PSFDD patients have a similar exercise tolerance as PSFN. Both groups have worse exercise tolerance than CDD. PSFDD and PSFN patients seem to experience a greater awareness of VE than CDD and patients with SHF.

Keywords: chronic heart failure,, ventilation

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