P1421 Patients with severe aortic regurgitation showed systolic dysfunction and increased stroke work despite preserved EF; clues for reconsidering optimal time point of surgery

Background

Current guidelines recommend surgery in patients with severe aortic regurgitation (AR) with clinical symptoms or subnormal ejection fraction (EF). Furthermore, surgery should be considered in patients with severe AR, preserved EF and increased left ventricular diameters (LVEDD >70mm, LVESD >50mm). The aim of the study was to investigate LV systolic function as well as mechanical energetics using non-invasive pressure-volume- and strain analysis in patients with severe AR and preserved EF as well as moderately dilated ventricles (LVEDD <70mm).

Methods and Results

Echocardiographic strain and single beat pressure-volume analyses were performed in patients with severe AR and moderately increased ventricular size (LVEDD < 70mm, EF >50% n = 39) as well as healthy, age-matched controls (n = 20) using echo-derived volume and arm-cuff blood pressure measurements. Load independent parameters of systolic contractile function like end-systolic elastance (Ees) and end-systolic volume at 100mmHg (ESV100) were calculated as well as stroke work ((SW) and total pressure volume area (PVA = SW + potential energy). Patients with AR demonstrated significant depression of systolic function beyond ejection fraction: global longitudinal strain was reduced compared to controls (-16 ±2.5% vs. -21.5 ±2%; p < 0.001). Accordingly load independent parameters of LV contractility like Ees (1.5mmHg/ml ±0.7 vs. 2.25mmHg/ml ±0.7; p < 0.001), ESV100 (65.7ml ±19.4 vs. 42.4ml ±19.8; p < 0.05) were reduced despite comparable ejection fractions (EF: 0.56% ±0.05 vs. 0.60% ±0.07 p = 0,10). End-diastolic volume of AR patients was markedly elevated (236ml ±90 vs. 136ml ±30; p < 0.001), while PVA (20470mmHg x ml ±10400 vs. 11907mmHg x ml ±2877; p < 0.01) and stroke work (13200mmHg x ml ±5700 vs. 7606 mmHG x ml ±2048; p< 0.01) were markedly elevated indicating waste of energy.

Conclusion

Patients with severe AR and moderately enhanced LV showed depressed values of contractility and waste of energy using more advanced parameters of LV systolic function although EF was preserved. The data may demonstrate that surgery is performed too late in many of those patients and may give clues for reconsidering guidelines to meet the optimal time point of surgery.

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A background Ca2+ entry pathway mediated by TRPC1/TRPC4 is critical for development of pathological cardiac remodelling

AIMS

Pathological cardiac hypertrophy is a major predictor for the development of cardiac diseases. It is associated with chronic neurohumoral stimulation and with altered cardiac Ca(2+) signalling in cardiomyocytes. TRPC proteins form agonist-induced cation channels, but their functional role for Ca(2+) homeostasis in cardiomyocytes during fast cytosolic Ca(2+) cycling and neurohumoral stimulation leading to hypertrophy is unknown.

METHODS AND RESULTS

In a systematic analysis of multiple knockout mice using fluorescence imaging of electrically paced adult ventricular cardiomyocytes and Mn(2+)-quench microfluorimetry, we identified a background Ca(2+) entry (BGCE) pathway that critically depends on TRPC1/C4 proteins but not others such as TRPC3/C6. Reduction of BGCE in TRPC1/C4-deficient cardiomyocytes lowers diastolic and systolic Ca(2+) concentrations both, under basal conditions and under neurohumoral stimulation without affecting cardiac contractility measured in isolated hearts and in vivo. Neurohumoral-induced cardiac hypertrophy as well as the expression of foetal genes (ANP, BNP) and genes regulated by Ca(2+)-dependent signalling (RCAN1-4, myomaxin) was reduced in TRPC1/C4 knockout (DKO), but not in TRPC1- or TRPC4-single knockout mice. Pressure overload-induced hypertrophy and interstitial fibrosis were both ameliorated in TRPC1/C4-DKO mice, whereas they did not show alterations in other cardiovascular parameters contributing to systemic neurohumoral-induced hypertrophy such as renin secretion and blood pressure.

CONCLUSIONS

The constitutively active TRPC1/C4-dependent BGCE fine-tunes Ca(2+) cycling in beating adult cardiomyocytes. TRPC1/C4-gene inactivation protects against development of maladaptive cardiac remodelling without altering cardiac or extracardiac functions contributing to this pathogenesis.