title: A relative value method for measuring and evaluating cardiac reserve.
abstract: BACKGROUND
  Although a very close relationship between the amplitude of the first heart sound (S1) and the cardiac contractility have been proven by previous studies, the absolute value of S1 can not be applied for evaluating cardiac contractility. However, we were able to devise some indicators with relative values for evaluating cardiac function.
  
  
  METHODS
  Tests were carried out on a varied group of volunteers. Four indicators were devised: (1) the increase of the amplitude of the first heart sound after accomplishing different exercise workloads, with respect to the amplitude of the first heart sound (S1)recorded at rest was defined as cardiac contractility change trend (CCCT). When the subjects completed the entire designed exercise workload (7000 J), the resulting CCCT was defined as CCCT(1); when only 1/4 of the designed exercise workload was completed, the result was defined as CCCT(1/4). (2) The ratio of S1 amplitude to S2 amplitude (S1/S2). (3) The ratio of S1 amplitude at tricuspid valve auscultation area to that at mitral auscultation area T1/M1 (4) the ratio of diastolic to systolic duration (D/S). Data were expressed as mean +/- SD.
  
  
  RESULTS
  CCCT(1/4) was 6.36 +/- 3.01 (n = 67), CCCT(1) was 10.36 +/- 4.2 (n = 33), S1/S2 was 1.89 +/- 0.94 (n = 140), T1/M1 was 1.44 +/- 0.99 (n = 144), and D/S was 1.68 +/- 0.27 (n = 172).
  
  
  CONCLUSIONS
  Using indicators CCCT(1/4) and CCCT(1) may be beneficial for evaluating cardiac contractility and cardiac reserve mobilization level, S1/S2 for considering the factor for hypotension, T1/M1 for evaluating the right heart load, and D/S for evaluating diastolic cardiac blood perfusion time.
authors.affiliation: Biomedical Engineering Department, Chongqing University, Chongqing 400044, China. xiaosz@cq.cnuninet.net
authors.forename: Shouzhong
authors.initials: S
authors.lastname: Xiao
authors.forename: Xingming
authors.initials: X
authors.lastname: Guo
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Sun
authors.forename: Zifu
authors.initials: Z
authors.lastname: Xiao
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003971:Diastole; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006326:Heart Auscultation / Q000379:methods*; D006331:Heart Diseases / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D006337:Heart Murmurs / Q000175:diagnosis; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000175:diagnosis; D009200:Myocardial Contraction / Q000502:physiology*; D010701:Phonocardiography; D012372:ROC Curve; D015996:Survival Rate; D013599:Systole / Q000502:physiology