Key result
Transient inferior vena cava balloon occlusion resulted in a significant increase in left ventricular twist from 11.67° to 16.17° (p < 0.004), demonstrating that peak systolic LV twist is load-dependent.
Why the study?
Does acute load reduction alter left ventricular twist and untwisting rate in a large animal model?
Does acute load reduction alter left ventricular twist and untwisting rate in a large animal model?
Absolute Event Rate: 16.17% vs 11.67%
p-value: p=<0.004
Left ventricular twist and untwisting rate are strongly load-dependent, indicating that serial clinical measurements of torsion must be interpreted in the context of loading conditions.
Caution against load-agnostic LV twist interpretation in serial assessments; leaves open translation from large-animal models to patients.
BACKGROUND: Left ventricular rotation and twist can be assessed noninvasively by speckle tracking echocardiography. We sought to characterize the effects of acute load change and change in inotropic state on rotation parameters as a measure of left ventricular (LV) contractility. METHODS: Seven anesthetised juvenile pigs were studied, using direct measurement of left ventricular pressure and volume and simultaneous transthoracic echocardiography. Transient inflation of an inferior vena cava balloon (IVCB) catheter produced controlled load reduction. First and last beats in the sequence of eight were analysed with speckle tracking (STE) during the load alteration and analysed for change in rotation/twist during controlled load alteration at same contractile status. Two pharmacological inotropic interventions were also included to examine the same hypothesis in additionally conditions of increased and decreased myocardial contractility in each animal. Paired comparisons were made for different load states using the Wilcoxon's Signed Rank test. RESULTS: The inferior vena cava balloon occlusion (IVCBO) load change compared for first to last beat resulted in LV twist increase (11.67° ±2.65° vs. 16.17° ±3.56° respectively, p < 0.004) during the load alteration and under adrenaline stimulation LV twist increase 12.56° ±5.1° vs. 16.57° ±4.6° (p < 0.013), and though increased, didn't reach significance in negative inotropic condition. Untwisting rate increased significantly at baseline from -41.7°/s ±41.6°/s vs.-122.6°/s ±55.8°/s (P < 0.039) and under adrenaline stimulation untwisting rate increased (-55.3°/s ±3.8°/s vs.-111.4°/s ±24.0°/s (p < 0.05), but did not systematically changed in negative inotropic condition. CONCLUSIONS: Peak systolic LV twist and peak early diastolic untwisting rate are load dependent. Differences in LV load should be included in the interpretation when serial measures of twist are compared.
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A’roch et al. (2012) studied Healthy (animal model) (n=7). Transient inferior vena cava balloon occlusion (load reduction) vs. Baseline (first beat prior to load reduction) was evaluated on Left ventricular twist (Twist_MAX) (p=<0.004). Transient inferior vena cava balloon occlusion resulted in a significant increase in left ventricular twist from 11.67° to 16.17° (p < 0.004), demonstrating that peak systolic LV twist is load-dependent.
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