What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Hypertrophic Cardiomyopathy (n=53). Intervention: Hypertrophic cardiomyopathy vs. Control subjects with structurally normal hearts. Primary outcome: Coronary flow reserve (p=0.01).

October 1, 2016Open Access

Mechanisms of Myocardial Ischemia in Hypertrophic Cardiomyopathy

Key Result

Patients with hypertrophic cardiomyopathy had a significantly lower coronary flow reserve (1.9 vs 2.7) and a larger backward compression wave during systole (38% vs 21%) compared to control subjects.

Study Design

Type

Cross-Sectional (n=53)

Multicenter

Yes

Structured PICO

What are the mechanisms underlying perfusion abnormalities in patients with hypertrophic cardiomyopathy compared to controls?

Population

33 patients with hypertrophic cardiomyopathy (HCM) and 20 control patients

Intervention

Simultaneous pressure and flow measurement in the proximal left anterior descending artery at rest and during hyperemia (wave intensity analysis) and quantitative first-pass perfusion cardiac magnetic resonance

Comparator

Control patients

Outcome

Coronary flow reserve and wave intensity parameters (backward compression wave, backward expansion wave)surrogate

In patients with HCM, perfusion abnormalities are driven by dynamic interactions including a large backward compression wave during systole due to compressive deformation of intramyocardial blood vessels.

Main Result

Absolute Event Rate: 1.9% vs 2.7%

p-value: p=0.01

Limitations

Recruited patients were symptomatic with a clinical indication for angiography, limiting generalizability to asymptomatic patients
Control subjects had risk factors for coronary disease and potential mild microvascular disease
Differences in medication use (beta-blockers, ACE inhibitors) between groups were not adjusted for
Findings cannot be generalized to pediatric or adolescent populations
Use of sum-of-squares estimate for wave speed introduces uncertainty into separated wave intensity calculations

Abstract

BACKGROUND: Angina is common in hypertrophic cardiomyopathy (HCM) and is associated with abnormal myocardial perfusion. Wave intensity analysis improves the understanding of the mechanics of myocardial ischemia. OBJECTIVES: Wave intensity analysis was used to describe the mechanisms underlying perfusion abnormalities in patients with HCM. METHODS: Simultaneous pressure and flow were measured in the proximal left anterior descending artery in 33 patients with HCM and 20 control patients at rest and during hyperemia, allowing calculation of wave intensity. Patients also underwent quantitative first-pass perfusion cardiac magnetic resonance to measure myocardial perfusion reserve. RESULTS: Patients with HCM had a lower coronary flow reserve than control subjects (1.9 ± 0.8 vs. 2.7 ± 0.9; p = 0.01). Coronary hemodynamics in HCM were characterized by a very large backward compression wave during systole (38 ± 11% vs. 21 ± 6%; p < 0.001) and a proportionately smaller backward expansion wave (27% ± 8% vs. 33 ± 6%; p = 0.006) compared with control subjects. Patients with severe left ventricular outflow tract obstruction had a bisferiens pressure waveform resulting in an additional proximally originating deceleration wave during systole. The proportion of waves acting to accelerate coronary flow increased with hyperemia, and the magnitude of change was proportional to the myocardial perfusion reserve (rho = 0.53; p < 0.01). CONCLUSIONS: Coronary flow in patients with HCM is deranged. Distally, compressive deformation of intramyocardial blood vessels during systole results in an abnormally large backward compression wave, whereas proximally, severe left ventricular outflow tract obstruction is associated with an additional deceleration wave. Perfusion abnormalities in HCM are not simply a consequence of supply/demand mismatch or remodeling of the intramyocardial blood vessels; they represent a dynamic interaction with the mechanics of myocardial ischemia that may be amenable to treatment.

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