title: Relation of isovolumic times after cardiac resynchronization therapy to improvement in exercise capacity.
abstract: Isovolumic times (IVTs) comprise a determinant of exercise capacity in cardiomyopathy. We postulated that an increase in exercise capacity after cardiac resynchronization therapy (CRT) might be related to a more efficient cardiac cycle due to decreasing IVTs and increased filling times. According to standard selection criteria, a CRT device was implanted in 52 patients (37 men; 69 +/- 8 years) with a QRS duration of 174 +/- 30 ms. The etiology was ischemic in 22 and idiopathic in 30 patients. A 6-minute walking test (MWT) and echocardiographic Doppler were performed before and 3 and 6 months after CRT. Timing cycles were obtained with echocardiographic Doppler. An improvement in MWT by >15% (responders) after 6 months of CRT was observed in 46% of patients. The MWT was moderately correlated with baseline time intervals (IVT r = -0.44, filling time r = 0.52), but not to baseline left ventricular ejection fraction (r = -0.06). However, change in the MWT after 3 and 6 months was best related to changes in IVT (r = -0.66 and -0.68, respectively). Receiver-operating characteristic curve analysis of baseline IVT showed that an IVT >29% predicted exercise response with a positive predictive value of 89% and a negative predictive value of 77%. In conclusion, improvement in exercise tolerance after CRT is associated with a decrease in prolonged IVT. Baseline IVT might be used as an adjunctive parameter for selecting symptomatic responders to CRT.
authors.affiliation: Department of Cardiology, Catharina Hospital, Eindhoven, The Netherlands.
authors.forename: Annemieke H M
authors.initials: AH
authors.lastname: Jansen
authors.forename: Kathinka H
authors.initials: KH
authors.lastname: Peels
authors.forename: Frank
authors.initials: F
authors.lastname: Bracke
authors.forename: Jan Melle
authors.initials: JM
authors.lastname: van Dantzig
authors.forename: Albert
authors.initials: A
authors.lastname: Meijer
authors.forename: Pepijn H
authors.initials: PH
authors.lastname: van der Voort
authors.forename: Berry
authors.initials: B
authors.lastname: van Gelder
authors.forename: Hendrikus H M
authors.initials: HH
authors.lastname: Korsten
authors.forename: Norbert M
authors.initials: NM
authors.lastname: van Hemel
mesh_terms: D000368:Aged; D002304:Cardiac Pacing, Artificial; D009202:Cardiomyopathies / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D015150:Echocardiography, Doppler; D004562:Electrocardiography; D017079:Exercise Tolerance; D006329:Heart Conduction System; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013318:Stroke Volume