Limitation of exercise tolerance in chronic heart failure: distinct effects of left Bundle-Branch block and coronary artery disease
Alison M. Duncan, MB, BS*,*,
Darrel P. Francis, MD*,
Derek G. Gibson, FRCP* and
Michael Y. Henein, MD, PhD, FACC*
* Department of Echocardiography, The Royal Brompton Hospital, London, United Kingdom
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Figure 1 Measurement of total isovolumic time (t-IVT) in a patient with dilated cardiomyopathy (aortic and mitral Doppler recordings superimposed). Total ejection time (ET) and total filling time (FT) are derived as the product of the corresponding time interval and heart rate, expressed in s/min. The t-IVT is then calculated as [60 – (total ejection time + total filling time)]. ET = 320 ms or 0.32 x 63 = 20 s/min. FT = 500 ms or 0.50 x 63 = 32 s/min. t-IVT = 60 – (20 + 32) = 8 s/min. ECG = electrocardiogram; PCG = phonocardiogram.
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Figure 2 Percentage predicted peak exercise capacity (VO2) in individual patients with dilated cardiomyopathy. Patients with neither coronary artery disease (CAD) nor left bundle branch block (LBBB) had the highest values for %peak VO2. Coronary artery disease reduced %predicted peak VO2, but patients with LBBB had the lowest values of all, irrespective of whether CAD was present.
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Figure 3 (Top) Correlation between resting total isovolumic time (t-IVT) and percentage predicted peak exercise capacity (VO2). When individual patients were considered as a single group, resting t-IVT correlated closely with %predicted peak VO2. Patients with left bundle branch block (LBBB) had the longest t-IVT at rest and the lowest %predicted peak VO2, irrespective of whether coronary artery disease (CAD) was present. (Bottom) Lack of correlation between left ventricular ejection fraction and %predicted peak VO2.
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