What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Nonobstructive Hypertrophic Cardiomyopathy (n=68). Intervention: Nonobstructive hypertrophic cardiomyopathy vs. Healthy controls. Primary outcome: Global longitudinal strain in the inner layer (p=<0.001).

January 1, 2015Open Access

Myocardial Shortening in 3 Orthogonal Directions and Its Transmural Variation in Patients With Nonobstructive Hypertrophic Cardiomyopathy

Q: What are the key findings of this study?

In patients with nonobstructive hypertrophic cardiomyopathy, longitudinal strain was reduced in all myocardial layers, while circumferential strain was reduced in mid and outer layers but preserved in the inner layer.

Key Result

In patients with nonobstructive hypertrophic cardiomyopathy, longitudinal strain was reduced in all myocardial layers, while circumferential strain was reduced in mid and outer layers but preserved in the inner layer.

Study Design

Type

Cross-Sectional (n=68)

Multicenter

Structured PICO

Are multidirectional and layer-specific myocardial strains reduced in patients with nonobstructive HCM compared to controls?

Population

68 subjects, comprising 41 patients with nonobstructive hypertrophic cardiomyopathy and 27 healthy controls, underwent speckle-tracking echocardiography to assess layer-specific myocardial strain.

Exposure

Speckle-tracking echocardiography

Comparator

Control subjects

Outcome

Segmental and global longitudinal strain (LS) and circumferential strain (CS) in the inner, mid, and outer layerssurrogate

In nonobstructive HCM, longitudinal strain is reduced across all myocardial layers and circumferential strain is reduced in mid and outer layers, while inner layer circumferential strain is preserved and correlates with LVEF.

Main Result

Absolute Event Rate: -10.3% vs -14.8%

p-value: p=<0.001

Limitations

Difficult to assume myocardial shortening in a particular direction represents only shortening of fibers oriented in the same direction due to complex interactions and myofibrillar disarray.
Wall stress was not taken into account because general formulae could not be used due to asymmetric LV hypertrophy.
20 of the 41 patients with HCM were taking a β-blocker, which might have affected myocardial contractility.
The theory regarding transmural variation in the impairment of circumferential shortening is purely speculative as force between layers cannot be measured noninvasively.

Abstract

BACKGROUND: Although longitudinal strain (LS) is known to be reduced in patients with hypertrophic cardiomyopathy (HCM), it has not been elucidated whether or not circumferential strain (CS) is reduced. We aimed to determine whether multidirectional and layer-specific myocardial strain is reduced in patients with nonobstructive HCM. METHODS AND RESULTS: Speckle-tracking echocardiography was performed in 41 HCM patients and 27 control subjects. Segmental and global LS and CS were measured in the inner, mid, and outer layers. Global LS was significantly lower in the HCM group than in controls in the inner (-10.3±2.9 vs. -14.8±2.0%, P<0.001), mid (-8.7±2.6 vs. -13.8±1.9%, P<0.001), and outer (-7.2±2.6 vs. -11.9±1.9%, P<0.001) layers. Global CS was preserved in the inner layer (-23.8±4.7 vs. -24.3±3.3%, P=0.69) but reduced in the mid (-10.3±3.1 vs. -13.3±2.5%, P<0.001) and outer layers (-6.7±2.3 vs. -8.6±2.3%, P=0.002). Differences in CS between the inner and outer layers correlated with segmental relative wall thickness (r=-0.20, P=0.002). Furthermore, only the absolute value of global CS in the inner layer positively correlated with left ventricular ejection fraction (r=0.32, P<0.01) among these multidirectional and layer-specific strains. CONCLUSIONS: In patients with HCM, not only the LS in all layers but also CS in the mid and outer layers was reduced, presumably reflecting impaired myocardial function. In contrast, CS in the inner layer was preserved, being associated with maintenance of chamber function.

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