title: Left ventricular hypercontractility and ST segment depression in patients with syndrome X.
abstract: OBJECTIVE
  This study was designed to assess the relation between rest left ventricular function and exercise capacity in patients with syndrome X.
  
  
  BACKGROUND
  Clinical observation has suggested that some patients with syndrome X have a high rest left ventricular ejection fraction. In this study we determined the relation between left ventricular ejection fraction and exercise capacity and the electrocardiographic (ECG) changes that develop on exercise.
  
  
  METHODS
  The pattern of left ventricular function, exercise capacity and 24-h ambulatory ECG monitoring were studied in 37 patients (9 men, 28 women; mean age 52 +/- 7 years) with syndrome X (angina with normal coronary arteries and a positive exercise test result). All patients had normal findings on echocardiogram and rest ECG. All treatment was discontinued for > or = 48 h. Left ventricular ejection fraction was determined by computerized analysis of the left ventricular angiogram. In patients with syndrome X, exercise duration and heart rate were measured at 1-mm ST segment depression and at peak exercise.
  
  
  RESULTS
  Left ventricular hypercontractility (ejection fraction > or = 80%) was observed in 12 patients (32%) (group 1), whereas 25 patients (68%) had normal left ventricular contraction (group 2). The time to 1-mm ST depression on exercise testing was significantly earlier in group 1 than in group 2 (5.13 +/- 1.03 vs. 10.76 +/- 0.63 min, respectively, p < 0.001). The magnitude of the ST segment depression at peak exercise was significantly greater in group 1 than in group 2 (2.03 +/- 0.2 vs. 1.33 +/- 0.05 mm, respectively, p < 0.001). The mean time for ST segment depression to normalize was significantly greater in group 1 than in group 2 (4.76 +/- 0.78 vs. 3.16 +/- 0.39 min, respectively, p < 0.05). Linear regression analysis of all patients with syndrome X showed a significant correlation between exercise duration and ejection fraction (r = 0.55, p < 0.001). The mean circadian variation of heart rate and episodes of ST segment depression on 24-h ambulatory ECG monitoring were similar in the two groups of patients.
  
  
  CONCLUSIONS
  These findings indicate that approximately one third of patients with chest pain, normal coronary angiograms and a positive exercise test have left ventricular hypercontractility, and this is associated with the development of ST segment depression at a lower heart rate and work load and a longer time to normalization of ST segment depression after exercise.
authors.affiliation: Cardiovascular Research Unit, Royal Postgraduate Medical School, Hammersmith Hospital, London, England, United Kingdom.
authors.forename: D
authors.initials: D
authors.lastname: Tousoulis
authors.forename: T
authors.initials: T
authors.lastname: Crake
authors.forename: D C
authors.initials: DC
authors.lastname: Lefroy
authors.forename: A R
authors.initials: AR
authors.lastname: Galassi
authors.forename: A
authors.initials: A
authors.lastname: Maseri
mesh_terms: D000328:Adult; D000368:Aged; D015716:Electrocardiography, Ambulatory; D005080:Exercise Test; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D017566:Microvascular Angina / Q000503:physiopathology*; D008875:Middle Aged; D013318:Stroke Volume / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*