Influence of afterload on left ventricular radial and longitudinal systolic functions: a two-dimensional strain imaging study.

AIMS: This study aimed to assess the influence of afterload alteration on radial (R) and longitudinal (L) left ventricular (LV) systolic regional functions. METHODS AND RESULTS: We analysed systolic myocardial function by two-dimensional strain (2D-S) and sonomicrometry (SS) in an experimental pig model of aortic banding. Both radial and longitudinal functions were analysed in six open-chest pigs under various loading conditions: baseline and graded aortic banding (subsequent increase in LV pressure of 10, 20, and 40 mmHg). Both systolic 2D-S(long) and 2D-S(rad) were significantly correlated with SS(long) and SS(rad) (r = 0.63, P < 0.001 and r = 0.65, P < 0.01, respectively). At a low increase in LV afterload, 2D-S(rad) was still preserved whereas 2D-S(long) significantly decreased. When LV afterload was subsequently increased, both 2D-S(rad) and 2D-S(long) significantly decreased. Difference in dependence to wall stress might explain these different behaviours. CONCLUSION: 2D-S shows a different response in longitudinal and radial functions to increased afterload. Longitudinal function is early impaired, whereas radial function remains preserved. This finding justifies the combined assessment of both radial and longitudinal regional myocardial functions to characterize myocardial dysfunction and might help to better identify the transition to heart failure in pressure-overload cardiomyopathy.

Instant centre frequency at anaesthetic induction--a new way to analyse sympathovagal balance.

The instant centre frequency (ICF) of RR interval has been proposed as a global index to analyse the sympathovagal interaction in the heart. The aim of this study was to assess the ICF during anaesthesia to test if it can reliably capture the neural control of the cardiovascular system. Twenty-four ASA II or III patients scheduled for cardiac surgery were included in the study. They were allocated in two groups: control, no treatment (group 1, n = 12), and beta-adrenergic blockade by atenolol (group 2, n = 12). Spectra of pulse interval series were computed with a time-frequency method and they were divided into: very low frequency (VLF, 0.000-0.040 Hz), low frequency (LF, 0.050-0.150 Hz) and high frequency (HF, 0.160-0.500 Hz). Normalized power was obtained by dividing the cumulative power within each frequency band (LF or HF) by the sum of LF and HF; the ratio of LF/HF was also calculated. Instant centre frequency is a time-varying parameter that the evolution along time of the gravity centrum of a local spectrum. All spectral indexes were recorded at the following time points: before induction, after induction and before intubation, during intubation, and after intubation. The atenolol group had lower normalized LF and the LF/HF ratio (P < 0.05) higher HF before induction; and lower LF/HF ratio after induction and before intubation (P < 0.05). The ICF was higher in atenolol group at all times. The ICF shifted towards HF frequency after induction and before intubation and shifted towards LF during intubation in both groups. The autonomic nervous system control on the heart through the interaction of sympathetic and parasympathetic reflex mechanisms could be studied by the ICF. The ICF may assess the autonomic cardiac modulation and may provide useful information for anaesthetic management.

Ginkgo biloba extract EGb 761 attenuates myocardial stunning in the pig heart.

Myocardial stunning, a transient contractile dysfunction that appears following a brief period of ischemia, is at least partly due to the production of oxygen-derived free radicals. The objective of the present study was to determine whether the Ginkgo biloba extract EGb761, which has antioxidant properties in vitro, can attenuate myocardial stunning in vivo. Forty-seven anesthetized open-chest farm pigs underwent 10 min of occlusion of the left anterior descending coronary artery (LAD), followed by 3 hours of reperfusion. They were pretreated with either physiological saline, 100 mg or 300 mg of EGb 761 (Protocol I) or 3 mg or 9 mg of ginkgolide B (GkB) (Protocol II). Contractile function was assessed by sonomicrometry. Both doses of EGb 761 significantly improved recovery of contractile function in the reperfused myocardium with segment shortening averaging 23 +/- 5 % of baseline values at 3 hours post-reflow in controls versus 81 +/- 10 % and 57 +/- 12 % in the EGb100 and EGb300 groups, respectively (p < 0.05 vs control in both cases). In contrast, neither dose of GkB improved functional recovery during reperfusion. ESR experiments revealed that EGb761 resulted in a 59 % decrease in myocardial spin-adduct release during reperfusion (p < 0.05 versus control and GkB groups). A significant 28 % decrease (p < 0.05 vs control group) was also obtained in GkB-treated animals. These results indicate that EGb 761 can attenuate myocardial stunning following a brief ischemic insult in the in situ pig heart by an effect that involves a decrease in the formation of free radicals. As the effect of EGb 761 on functional recovery cannot be explained by the presence of GkB, the beneficial action of the extract on myocardial stunning likely involves complementary effects of both its non-ginkgolide and ginkgolide constituents.