Loss of diastolic time as a mechanism of exercise-induced diastolic dysfunction in dilated cardiomyopathy.
BACKGROUND
Cardiac performance can be characterized in terms of the relative duration of left ventricular systole and diastole. Little is known about exercise-induced abnormalities of the systolic-diastolic phase proportion and its impact on hemodynamic variables in patients with idiopathic dilated cardiomyopathy (IDCM).


METHODS
The phases of the cardiac cycle were derived with high temporal resolution from the left ventricular time-activity curve simultaneous with hemodynamic measurements. In patients with IDCM, the loss of diastolic time (LDT) per beat was quantified using a regression equation obtained from a healthy control group (n = 26). According to the median LDT at peak exercise, patients were divided into 2 subgroups: subgroup A with an LDT <or=22 milliseconds (n = 28) and subgroup B with an LDT >22 milliseconds (n = 27).


RESULTS
The relative duration of left ventricular systole was increased in patients with IDCM during peak exercise compared to healthy subjects (29.3 vs 26.7 s/min, P < .02). This abnormality translated into a significant LDT when observed, and predicted values of diastolic time were compared. Subgroup B patients had a higher increment in mean pulmonary capillary wedge pressure but a smaller increase in stroke volume index from rest to peak exercise (14.3 vs 8.6 mm Hg [P = .007] and 12.5 vs 7.2 mL/m(2) [P = .04]) compared to subgroup A patients.


CONCLUSIONS
An abnormal shortening of diastolic time during exercise can restrict left ventricular filling to an extent that is sufficient to limit left ventricular stroke volume reserve and to cause pulmonary congestion.
Department of Cardiology and Angiology, University of Bochum, Germany. gunnar.plehn@ruhr-uni-bochum.de
Gunnar
G
Plehn
Julia
J
Vormbrock
Christian
C
Perings
Sebastian
S
Machnick
Christian
C
Zuehlke
Hans-Joachim
HJ
Trappe
Axel
A
Meissner
D000328:Adult; D002311:Cardiomyopathy, Dilated / Q000503:physiopathology*; D016022:Case-Control Studies; D003971:Diastole; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*