Transoesophageal echocardiography during coronary artery bypass procedures: impact on surgical planning

INTRODUCTION

Intraoperative transesophageal echocardiography (iTEE) is widely accepted and routinely used during heart valve surgery. However, the impact of iTEE among patients undergoing coronary artery bypass grafting (CABG) is less well documented. In this study, we aim to define the impact of iTEE in patients undergoing myocardial revascularization for severe coronary artery disease.

METHODS

We analyzed clinical data and preoperative and intraoperative echocardiograms of all adults who underwent on pump coronary bypass and iTEE between January 2008 and December 2008.

RESULTS

521 patients (mean age 69±14 years) were studied. New prebypass findings were obtained in 82 (15.7%) patients: in 62 (11.9%) of these patients, this information changed the surgical plan. New postbypass findings were obtained in 8 patients (1.5%) and the surgical plan was altered in 4 patients (0.7%).

CONCLUSIONS

Overall new findings were obtained in 90 patients (17.2%) and the surgical plan was altered in 66 patients (12.6%). These data support the routine use of iTEE among patients undergoing surgical myocardial revascularization.

Effect of levosimendan on ventriculo-arterial coupling in patients with ischemic cardiomyopathy

BACKGROUND

Levosimendan, a novel calcium sensitizer, enhances myocardial contractility without affecting intracellular calcium concentration. It also dilates peripheral arterial vessels by acting on ATP-dependent K(+) channels. Ventriculo-arterial coupling, the relationship between myocardial contractility and the arterial system, describes the efficiency of the cardiovascular system by analysing the relationship between myocardial contractility expressed by ventricular elastance (E(es)) and arterial elastance (E(a)). The aim of this prospective clinical investigation was to evaluate the effects of levosimendan on ventriculo-arterial coupling in patients with ischemic cardiomyopathy.

METHODS

Fifteen patients with stable angina and left ventricular dysfunction underwent elective coronary surgery. Before surgery started, ventriculo-arterial coupling and several variables of cardiovascular performance were assessed by invasive monitoring and transoesophageal echocardiography before and after administration of levosimendan (12 mug/kg bolus) in coronary patients under general anesthesia.

RESULTS

The cardiac index and ejection fraction increased significantly [from 1.92 +/- 0.4 to 2.1 +/- 0.4 l/min/m(2) (P = 0.0004) and from 31% +/- 6 to 40% +/- 9 (P = 0.001), respectively], while mean arterial pressure and systemic vascular resistances decreased significantly [from 83 +/- 10 to 72 +/- 5 mmHg (P = 0.0016) and from 997 +/- 341 to 855 +/- 324 dyne s/cm(5) (P = 0.0002), respectively]. After administration of levosimendan, E(a) decreased significantly (from 4.3 +/- 1.8 to 3.2 +/- 1.3 mmHg/ml/m(2), P= 0.005), while E(es) significantly increased (from 2.8 +/- 1.6 to 4.4 +/- 2.3 mmHg/ml/m(2), P= 0.05); as a result, E(a)/E(es) decreased significantly (from 1.76 +/- 1 to 0.83 +/- 0.2, P= 0.002).

CONCLUSION

Levosimendan improves ventriculo-arterial coupling and cardiovascular performance in coronary patients with left ventricular dysfunction by enhancing myocardial contractility and reducing arterial elastance.

Right ventricular failure: physiology and assessment

Right ventricular function can be altered in several disease states involving lungs and heart. Severe right ventricular dysfunction is a major determinant of outcome in such situations, and may strongly influence clinical management. The complex geometry of the right ventricle and the different physiology with respect to the left ventricle make the right ventricular failure difficult to define and assess. The response to increased afterload is the main determinant of right ventricle physiology in pathologic conditions. This consists of right ventricular hypertrophy and enlargement, with reduced coronary blood flow to the right ventricular wall, dilation of tricuspid annulus and displacement of interventricular septum. This latter change involves the left ventricular diastolic function, which is reduced by leftward septal shifting. In right ventricle myocardial ischemia and infarction the primum movens of altered right ventricular function is not an increase in afterload, but the ischemic involvement of the right ventricle, more often in the setting of an inferior acute myocardial infarction. The assessment of right ventricular failure is based on thermodilution by pulmonary artery catheter, contrast and radionuclide ventriculography, echocardiography, and magnetic resonance. Among these techniques, thermodilution and echocardiography play a relevant role in clinical scenarios, being readily available and feasible bedside.

Target controlled infusion: TCI

Progress in computing technology has allowed the development of target controlled infusion devices, with drugs delivered to achieve specific predicted target blood drug concentrations. Target controlled infusion (TCI) system has been developed as a standardised infusion system for the administration of opioids, propofol and other anaesthetics by target controlled infusion. A set of pharmacokinetic parameters has been selected using computer simulation of a known infusion scheme. The selected model is incorporated into a computer-compatible infusion pump. Clinical trials with such systems have provided appropriate target concentrations for the administration of target controlled infusion of anaesthetic drugs. The technique of TCI strongly influences the development of intravenous anaesthesia and opens a scenario of new and exciting applications in peri-operative anaesthetic management. The launch of ''Diprifusor'' as the first commercially available TCI system for propofol was the cornerstone of a successful research period within the last decade, which evaluated the pharmacokinetic foundations of computer assisted intravenous drug delivery. Nowadays TCI technology is becoming a part of routine anaesthesia technique for the practitioner rather than a research tool for specialists and those who are enthusiasts of intravenous anaesthesia. Besides clinical application in anaesthesia, target controlled systems will play a significant role as research tools in the evaluation of drug interactions in anaesthesia and in the development of new control techniques for the administration of sedative and analgesic drugs in the peri-operative period.

Reduced compliance of left ventricle

Diastolic function is essential for efficient systolic performance. A normal diastole allows left ventricle (LV) filling to occur under normal intracavitary pressure. It is an energy dependent process, as such affected by ischemia. Several factors influence diastolic function of the LV: the mitral valve area, the gradient between atrium and ventricle, LV relaxation and compliance, atrial compliance, the presence of sinus rhythm, the end-systolic volume. Echocardiography is the principal diagnostic tool to assess LV diastolic function noninvasively in clinical practice. Doppler evaluation allows to analyse each phase of LV diastole through measurement of transmitral and pulmonary veins flows velocities. Tissue Doppler echocardiography and color M-mode Doppler have also been introduced in the study of diastole. The use of echocardiography in the setting of diastolic dysfunction in ICU and operatory room has relevant implications in the management of haemodynamic instability, in vasoactive d rugs titration, in the detection of myocardial ischemia, and in performing prognostic stratification. These information can guide the management of cardiac patients undergoing cardiac and non cardiac surgery, in the perioperative phase, as well as in the management of critical ICU patients. On this basis evaluating the LV filling properties can contribute to improve the quality of treatments in such challenging situations.