title: Impact of cardiac resynchronisation therapy on adaptation of circulatory and respiratory systems to exercise assessed by cardiopulmonary exercise test in patients with chronic heart failure.
abstract: BACKGROUND
  Cardiac resynchronisation therapy (CRT) has become a valuable therapeutic tool in patients with advanced chronic heart failure (CHF). The search for optimal methods for the assessment of CRT efficacy is still underway.
  
  
  OBJECTIVE
  To evaluate the impact of implantation of CRT devices in patients with CHF on adaptation of circulatory and respiratory systems to maximal exercise assessed by cardiopulmonary exercise tests (CPX) and 6-minute walking tests (6MWT).
  
  
  METHODS
  We investigated 27 patients (22 males, 5 females, 61.2+/-9.1 years) with a CRT device implanted due to advanced CHF, which resulted from ischaemic or dilated cardiomyopathy. All patients before implantation underwent echocardiography, CPX with expired gas analysis and 6MWT. Investigations were repeated at 3-6 months after CRT implantation. In CPX we evaluated peak oxygen uptake (peak VO2), oxygen pulse, maximal minute ventilation-carbon dioxide production (VE/VCO2 (max)), and its slope (VE/VCO2 slope) and VE/VO2 slope, VO2 in anaerobic threshold (AT), and cardiac and respiratory reserve. In 6MWT we evaluated walking distance and heart rate and blood pressure response to exercise.
  
  
  RESULTS
  We noted statistically higher mean peak VO2 after CRT implantation in the studied group: 11.34+/-3.38 vs. 14.56+/-3.99 ml/kg/min (p<0.0001) and 1.01 +/-0.44 vs. 1.4+/-0.55 l/min (p=0.003) and higher values of expired CO2: 1.00+/-0.43 vs. 1.43+/-0.67 l/min (p=0.004). The O2 pulse rose from 9.65+/-3.39 to 13.23+/-5.43 ml/beat (p=0.015). We also observed a significant reduction of VE/VCO2 slope from 42.34+/-13.35 before CRT to 34.77+/-6.04 after CRT (p=0.0196) and a significant decrease of VE/VO2 slope from 41.32 +/-15.46 to 34.01+/-6.27 (p=0.037). VE/VCO2 (max) fell from 58.02+/-15.86 to 50.1+/-13.14 (p=0.009). Patients estimated their dyspnoea on the Borg scale at peak exercise at 4.75+/-0.75 points before CRT and at 3.67+/-1.15 points (p=0.002) after CRT. Patients could walk a longer distance during 6MWT than before CRT (367+/-154.9 vs. 231.1+/-170.3 m, p<0.001).
  
  
  CONCLUSIONS
  Cardiac resynchronisation therapy improves exercise tolerance measured by means of CPX and 6MWT, improves respiratory system efficiency and restores its adaptive mechanisms during exercise in patients with advanced CHF. Better exercise adaptation after CRT may be objectively measured with CPX parameters, and correlates with improvement of clinical symptoms. CPX seems to be a very helpful tool in assessing the results of CRT.
authors.affiliation: 2nd Department of Ishaemic Heart Disease, National Institute of Cardiology, Warsaw, Poland. tchwyczko@ikard.pl
authors.forename: Tomasz
authors.initials: T
authors.lastname: Chwyczko
authors.forename: Maciej
authors.initials: M
authors.lastname: Sterliński
authors.forename: Aleksander
authors.initials: A
authors.lastname: Maciag
authors.forename: Bohdan
authors.initials: B
authors.lastname: Firek
authors.forename: Andrada
authors.initials: A
authors.lastname: Labecka
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Jankowska
authors.forename: Marek
authors.initials: M
authors.lastname: Kośmicki
authors.forename: Ilona
authors.initials: I
authors.lastname: Kowalik
authors.forename: Beata
authors.initials: B
authors.lastname: Malczewska
authors.forename: Hanna
authors.initials: H
authors.lastname: Szwed
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D002908:Chronic Disease; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D012720:Severity of Illness Index; D016896:Treatment Outcome; D016138:Walking