Volatile anesthetic effects on ischemic myocardium

Intraoperative Coronary Spasm: A Potential Case of Vasospastic Angina

Prinzmetal's angina typically features spasms of the coronary arteries due to the hyperreactivity of the vascular smooth muscle cells of the vessels to a nonspecific stimulus. Reports of coronary spasm during general anesthesia are rare, but in such cases, diagnosis is suggested by a framework of angina at rest and changes in the electrocardiogram (ECG) or coronary reactivity tests with ergonovine or acetylcholine. The present study describes a case of coronary spasm induced by general anesthesia associated with several cardiovascular risk factors and the usage of vasoactive drugs that was documented by angiography without using stimulating drugs and treated with intracoronary nitroglycerin. The patient was a 58-year-old male who was designated for carotid endarterectomy due to the stenosis (70%) of the right internal carotid artery by an atheromatous plaque after visiting the emergency department with a sensorimotor deficit in the left upper limb and bifrontal headaches with sudden onset. During the surgical intervention, after the administration of 10 mg of intravenous ephedrine, cardiorespiratory arrest occurred, with alternation between defibrillable and non-defibrillable heart paces. After the recovery of spontaneous circulation after 50 minutes of resuscitation maneuvers, the patient was transported to the hemodynamics laboratory, where there were recurrent episodes of ventricular fibrillation during the angioplasty of the anterior descending artery. After direct stent implantation, pre- and post-stent spasms were verified and reversed after the administration of intracardiac nitroglycerin. The spasm was a possible complication of anesthesia and responded to treatment with nitrates and calcium channel blockers. We would like to emphasize the importance of cardiac monitoring during surgery and anesthesia.

Mice display sex differences in halothane-induced polymorphic ventricular tachycardia

BACKGROUND

Molecularly engineered mice are extensively used as models of cardiovascular diseases, yet little is known about sex differences in the electrophysiology of mouse hearts.

METHODS AND RESULTS

This study investigated the influence of sex on drug-induced polymorphic ventricular tachycardia (PVT) in Langendorff-perfused male and female mice hearts (n=54) by injecting a bolus of halothane (1.75 mmol/L) in the perfusate while recording ECGs or optical action potentials (APs). There were no statistically significant differences between male and female hearts (n=54) with respect to mean RR (193+/-5 ms), PR (47+/-1 ms), QT intervals (101+/-3 ms), optical AP durations (APD(75)=23.11+/-4.2 ms), dispersion of refractory periods, and conduction velocities (n=5 male and 5 female). Halothane induced PVTs lasting a mean duration of 90 seconds; in female hearts, 55% of PVTs lasted longer than the median, whereas in male hearts 17% exceeded the mean (P<0.05). The total duration of PVTs exposed a marked sex difference, 378+/-144 seconds in female versus 27+/-10 seconds in male hearts (P<0.05). In optically mapped male hearts, halothane reduced APD(75) (17.61+/-1.6 ms) and then elicited VTs (n=6 of 6), but in female hearts, halothane elicited PVTs (n=1 of 6) or arrested the hearts (n=5 of 6). Except for KCNE1, Northern blots (KCNQ1, MERG, Kv1.5, connexins 40 and 43, TREK1, and TASK1) did not detect sex differences.

CONCLUSIONS

This mouse model reveals sex difference in response to a pharmacological challenge yet does not display sex differences in standard electrophysiological parameters. Differences in KCNE1 may contribute to sex differences uncovered by halothane.

Opposite effects of halothane on guinea-pig ventricular action potential duration

Halothane protects the heart against the reperfusion injury observed after an ischemia. In ischemic or anoxic conditions, a large ATP-sensitive K(+) (K(ATP)) conductance is supposed to provide an endogenous protection to the myocardium. In this study, we tested the possibility that halothane acted by modulating this conductance. Isolated guinea-pig cardiomyocytes were successively studied in current clamp and in voltage-clamp conditions. Action potentials regulation by halothane was tested in control conditions and in situations where the K(ATP) channels were activated. In control conditions, halothane decreased action potential duration of myocytes but did not significantly alter the inward rectifying K(+) current. Conversely, halothane lengthened action potential of cells in which the K(ATP) conductance was activated, by inhibiting the K(ATP) current. In ischemic conditions, simultaneous shortening of long action potentials and lengthening of shortened ones would be expected to homogenize the absolute refractory period at the border between normoxic and anoxic zones. This effect, together with a decrease in calcium load, could protect the myocardium against re-entrant arrhythmias.