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Left ventricular regional relaxation and its nonuniformity in hypertrophic nonobstructive cardiomyopathy
W Hayashida1, T Kumada, F Kohno
1Department of Internal Medicine, Faculty of Medicine, Kyoto University, Japan.
Insights
Regional nonuniformity in left ventricular (LV) relaxation is linked to hypertrophic cardiomyopathy (HCM). This study found impaired LV relaxation and regional differences in HCM patients, suggesting a connection between nonuniformity and disease severity.
Area of Science:
- Cardiology
- Biomedical Engineering
- Physiology
Background:
- Regional nonuniformity is implicated in impaired left ventricular (LV) relaxation in cardiac diseases.
- Hypertrophic cardiomyopathy (HCM) is a condition affecting the heart muscle.
Purpose of the Study:
- To evaluate global and regional LV relaxation in patients with nonobstructive HCM.
- To investigate the relationship between regional wall stress and LV relaxation dynamics in HCM.
Main Methods:
- Simultaneous left ventriculography and pressure micromanometry were performed in 10 controls and 11 nonobstructive HCM patients.
- LV silhouettes were divided into regions to compute regional wall stress during isovolumic relaxation.
- Key parameters including isovolumic relaxation time (IRT) and time constant of LV pressure decrease (Tp) were measured.
Main Results:
- HCM patients exhibited prolonged IRT and Tp, and altered dP/dt patterns, indicating impaired LV relaxation.
- End-systolic regional wall stress was reduced, and the time constant of regional stress decrease (Tst) was prolonged in HCM patients.
- A greater coefficient of variation for Tst in HCM patients demonstrated significant regional nonuniformity in LV relaxation.
Conclusions:
- Regional nonuniformity in Tst directly correlates with global LV relaxation parameters (Tp, IRT) and dP/dt(20/60) in HCM.
- Impaired LV relaxation in HCM is closely associated with regional variations in relaxation dynamics.
- These findings highlight the importance of regional analysis in understanding HCM pathophysiology.
Background:
Regional nonuniformity has been suggested to be closely related to left ventricular (LV) relaxation in diseased heart. The purpose of the present study was to assess LV global and regional relaxation in patients with nonobstructive hypertrophic cardiomyopathy (HCM).
Methods And Results:
Left ventriculography was conducted simultaneously with pressure micromanometry in 10 normal control subjects and 11 patients with nonobstructive HCM. LV silhouettes in the right anterior oblique projection were divided into eight regions, and regional wall stress during isovolumic relaxation was computed for six regions from the midventricle to the apex. In HCM patients, isovolumic relaxation time (IRT) and the time constant of LV pressure decrease (Tp) were greater than in control subjects (IRT, 84 +/- 13 versus 66 +/- 6 msec; Tp, 51 +/- 8 versus 36 +/- 5 msec, respectively; p less than 0.01). In HCM patients, the (-)dP/dt upstroke pattern was convex-downward, and dP/dt(20/60), the ratio of dP/dt values 20 and 60 msec after peak (-)dP/dt, was less than in control subjects (1.46 +/- 0.16 versus 2.15 +/- 0.14, p less than 0.01). These findings suggest that there is impaired LV relaxation in HCM patients. End-systolic regional wall stress was lower, and the time constant of regional stress decrease (Tst) was prolonged for each region in HCM patients compared with control subjects. In the HCM group, Tst tended to be more prolonged in regions with increased wall thickness than in regions with normal wall thickness (60 +/- 15 versus 50 +/- 11 msec, p less than 0.01). The coefficient of variation for Tst values in six areas of the left ventricle was calculated in each subject and was greater in HCM patients than in control subjects (13 +/- 7% versus 7 +/- 3%, p less than 0.05), indicating regional nonuniformity in Tst during isovolumic relaxation in HCM patients.
Conclusions:
Significant correlations existed between the coefficients of variation for Tst and Tp (r = 0.80, p less than 0.01), IRT (r = 0.79, p less than 0.01), and dP/dt(20/60) (r = -0.67, p less than 0.05) in the HCM group. Thus, regional nonuniformity is closely related to the impairment of LV relaxation in HCM.