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  • Title: Loss of diastolic time as a mechanism of exercise-induced diastolic dysfunction in dilated cardiomyopathy.
    Author: Plehn G, Vormbrock J, Perings C, Machnick S, Zuehlke C, Trappe HJ, Meissner A.
    Journal: Am Heart J; 2008 Jun; 155(6):1013-9. PubMed ID: 18513513.
    Abstract:
    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. CONCLUSION: 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.
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