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Preservation of exercise capacity and lack of peripheral changes in asymptomatic patients with severely impaired left
D Harrington1, S D Anker, A J Coats
1Cardiology Department, Kent and Sussex Hospital, Tunbridge Wells, Kent, UK.
Insights
Asymptomatic patients with severe left ventricular dysfunction may maintain normal exercise capacity and exhibit no peripheral changes. Peripheral factors, not just left ventricular function, significantly influence exercise capacity.
Area of Science:
- Cardiology
- Exercise Physiology
- Clinical Investigation
Background:
- Severe left ventricular dysfunction typically leads to reduced exercise capacity.
- Peripheral adaptations are often implicated in exercise limitation in heart failure patients.
Purpose of the Study:
- To investigate peripheral physiological changes in asymptomatic individuals with severe left ventricular dysfunction.
- To compare these changes with symptomatic patients and healthy controls.
Main Methods:
- Studied 9 asymptomatic and 9 symptomatic patients (left ventricular ejection fraction <25%) against 26 controls.
- Assessed exercise capacity, leg blood flow, respiratory muscle strength, quadriceps strength, and muscle fatigue.
- Measured thigh muscle cross-sectional area using CT scans.
Main Results:
- A graded increase in peak oxygen consumption was observed from symptomatic to asymptomatic to control groups (P<0.0001).
- Significant variations existed across groups in muscle strength, endurance, muscle area, blood flow, and respiratory strength (P<0.05).
- No significant differences were found when comparing asymptomatic patients to controls.
Conclusions:
- Severe left ventricular dysfunction does not necessarily preclude normal exercise capacity or the absence of peripheral changes.
- Exercise capacity appears to be influenced by peripheral factors, independent of left ventricular function severity.
Aims:
To establish the extent, if any, of peripheral changes in asymptomatic patients with severe left ventricular dysfunction. METHODS ANS RESULTS: Nine asymptomatic and nine symptomatic patients with left ventricular ejection fraction, <25%, matched for age and left ventricular ejection fraction (asymptomatic vs symptomatic, age: 52+/-1.5 vs 55.9+/-2.5 years [Mean+/-SEM], left ventricular ejection fraction: 16+/-2 vs 19+/-2%P=0.23 and 0.48, respectively) were studied and compared with 26 age-matched normal controls. We assessed exercise capacity, leg blood flow (occlusion plethysmography), respiratory muscle strength, quadriceps maximal isometric strength, fatigue and CT cross-sectional muscle area at mid thigh. Fatigue was expressed as the percentage reduction in maximal strength following a 20 min fatiguing protocol. There was a graded increase in peak oxygen consumption comparing symptomatic, asymptomatic and control groups (16.6+/-1.3 vs 27.1+/-1.6 vs 32.8+/-1.3 ml x min(-1) x kg(-1)respectively, ANOVA P<0.0001). Between the three groups there was significant variation in muscle strength (P<0.0001), endurance (P=0.0002) and cross-sectional area (P=0.0003) and in peak blood flow (P=0.027) and respiratory muscle strength (P<0.05). When asymptomatic patients and controls were compared no significant differences existed.
Conclusions:
Patients with severe left ventricular dysfunction may have near normal exercise capacity and no peripheral changes. Exercise capacity may depend less upon left ventricular function than on the presence or absence of peripheral factors.
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