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Differences in the Impact of Left Ventricular Outflow Tract Obstruction on Intraventricular Pressure Gradient in
Miki Hirose1, Momoko Watanabe2, Aki Takeuchi1
1Veterinary Teaching Hospital, Tokyo University of Agriculture and Technology, Fuchu 183-0054, Tokyo, Japan.
Insights
The intraventricular pressure gradient (IVPG) may reveal diastolic impairment in cats with obstructive hypertrophic cardiomyopathy (HCM). This novel index, measured via color M-mode, offers insights beyond conventional echocardiography for feline heart disease.
Area of Science:
- Veterinary Cardiology
- Echocardiography
- Feline Medicine
Background:
- Hypertrophic cardiomyopathy (HCM) is a prevalent cardiac condition in cats, often leading to heart failure due to diastolic dysfunction.
- HCM in cats is categorized as obstructive or non-obstructive, based on the presence of outflow tract obstruction.
- Traditional assessment of diastolic function relies on invasive methods or echocardiographic indices that may be limited.
Purpose of the Study:
- To evaluate the utility of the intraventricular pressure gradient (IVPG) measured by color M-mode echocardiography (CMM) for assessing diastolic impairment in cats with obstructive hypertrophic cardiomyopathy (HOCM).
- To determine if CMM-derived IVPG can detect pathological changes not evident with conventional echocardiographic parameters.
Main Methods:
- A study involving 10 healthy control cats and 18 cats diagnosed with HOCM.
- Non-invasive assessment of diastolic function using CMM to measure intraventricular pressure differences (IVPD) and calculate the IVPG index.
- Comparison of IVPG values between the HOCM group and the control group.
Main Results:
- The basal IVPG was significantly increased in cats with HOCM compared to healthy controls.
- No severe left atrial enlargement was noted in the HOCM group, suggesting the IVPG increase is not solely due to this factor.
- The elevated IVPG in HOCM may indicate indirect elevation of left atrial pressure, secondary to left ventricular outflow tract obstruction.
Conclusions:
- The CMM-derived IVPG is a valuable non-invasive index for detecting diastolic impairment in feline obstructive hypertrophic cardiomyopathy.
- The increased IVPG in HOCM reflects pathological effects of left ventricular outflow tract obstruction, offering a distinct perspective from conventional echocardiographic indices.
- Evaluating IVPG provides a useful method for assessing cardiac function in cats with HOCM, complementing existing diagnostic tools.
Abstract:
Hypertrophic cardiomyopathy (HCM) is a common form of cardiomyopathy in cats, and heart failure occurs as diastolic dysfunction progresses. HCM in cats is broadly classified as non-obstructive and obstructive hypertrophic cardiomyopathy, depending on the presence or absence of outflow tract obstruction. Measurement of the intraventricular pressure differences (IVPD) using color M-mode (CMM) has attracted attention as a reliable diastolic index as it correlates with catheterization, the gold standard for the assessment of diastolic performance. Because IVPD is affected by the size of the heart, the intraventricular pressure gradient (IVPG) index, which is unaffected by heart size, is by calculated by dividing IVPD by LV length. In the present study, CMM IVPG was used to non-invasively assess diastolic impairment in cats with obstructive hypertrophic cardiomyopathy. This study was conducted on 10 control cats and 18 cats in the HCM group. Although no severe left atrial enlargement was observed in the HCM group, the basal IVPG was significantly increased in the HOCM group compared to the control group. Although IVPD typically suggests impaired diastolic function and reduced ventricular compliance, the significant increase observed in the HOCM group compared to controls may suggest an indirect elevation in left atrial pressure, likely secondary to left ventricular outflow tract obstruction. The increase in IVPG in HOCM, as shown in this study, is a pathological effect of left ventricular outflow tract obstruction that cannot be detected by conventional echocardiographic indices, and evaluating IVPG is useful to evaluate cardiac function from a perspective that differs from conventional methods.
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