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Impaired exercise capacity in heart transplant recipients during aerobic exercise involving a small muscle mass
Author(s) -
Jendzjowsky N,
Tomczak C,
Lawrance R,
Riess K,
Taylor D,
Warburton D,
Tymchak W,
Haykowsky M
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a574-b
Subject(s) - aerobic exercise , cardiology , medicine , heart rate , stroke volume , vo2 max , cardiac output , impedance cardiography , vascular resistance , blood pressure , cardiac function curve , heart failure
Background: Heart transplant recipients (HTR) have impaired exercise tolerance when performing aerobic exercise involving a large muscle mass. Aim: To assess cardiac function and reserve during small muscle mass aerobic exercise in 5 clinically stable HTR (53±6 yrs) and 5 healthy controls (HC 53±7 yrs). Subjects performed unilateral knee extensor exercise (UKE, 3 watts·min −1 ) with expired gas analysis, impedance cardiography, and cuff blood pressure to measure: heart rate (HR); stroke volume (SV); cardiac output (Q), oxygen consumption (VO 2 ); arteriovenous oxygen difference (a‐vO 2diff ); mean arterial pressure (MAP) and systemic vascular resistance (SVR). Peak exercise and reserve function (peak – rest) data are presented. Results: Peak VO 2 (HTR: 0.9±0.2 vs HC: 1.6±0.5 L·min −1 ), Q (HTR: 9.4±1 vs HC: 12.1±2 L·min −1 ), SV (78±4 vs HC: 95±12 ml·beat −1 ) and a‐vO 2diff (HTR: 9.8±1.6 vs HC: 12.7±2.3 ml·100ml −1 ) were significantly lower in HTR vs. HC. The lower VO 2 reserve in HTR (0.6±0.2 vs HC 1.3±0.5 L·min −1 p<.05) was due to a blunted HR (HTR: 27±11 vs HC: 52±27 beats·min −1 p=.09), Q (HTR: 3.8±0.9 vs HC: 6.4±2.0 L·min −1 p<.05) and a‐vO 2diff reserve (HTR: 4.1±0.7 vs HC: 7.4±2.5 ml·100ml −1 p<.05). Peak HR, MAP, SVR and reserve SV, MAP and SVR were not different between groups. Conclusion: HTR have reduced VO 2peak during UKE. The impaired VO 2peak and VO 2 reserve during UKE is due to a blunted Q and a‐vO 2diff reserve resulting in reduced oxygen delivery and utilization by the active muscles.