Acute ventricular wall motion heterogeneity. A valuable but imperfect index of myocardial ischemia

Hemodynamic effects of portal triad clamping with and without pneumoperitoneum: an echocardiographic study

The decrease of cardiac index observed during portal triad clamping (PTC) with and without pneumoperitoneum has been studied only with right heart catheterization. To better understand this decrease of cardiac index, we investigated the balance between the adequacy of preload and the ability of the heart to pump against an increased afterload, by using transesophageal echocardiography. Ten patients with PTC performed during laparoscopy and 10 with PTC performed during laparotomy were studied. Five minutes after PTC, the stroke volume, the left ventricular (LV) fractional area change (FAC), and the LV end-systolic wall stress (LVESWS) were measured as the conventional hemodynamic variables. Regional wall motion abnormalities (RWMA) were also recorded. In the laparotomy group, LV end-diastolic area decreased, and LVESWS did not increase significantly. FAC remained stable, and one patient developed RWMA. In the laparoscopic group, LV end-diastolic area remained stable, and LVESWS increased. FAC decreased significantly, and five patients developed RWMA. A decrease in preload was the main important change in the laparotomy group, and in the laparoscopic group a decrease in LV function was demonstrated that was likely a consequence of decreased LV preload and increased LV afterload. However, these did not necessitate stopping the procedure or releasing PTC in these study patients without cardiac disease.

Acute hypovolemia may cause segmental wall motion abnormalities in the absence of myocardial ischemia

New segmental wall motion abnormalities (SWMA) detected by echocardiography are considered sensitive and specific markers of myocardial ischemia. However, we have observed new SWMA during pacing-induced reductions in left ventricular filling, which resolved immediately with cessation of the atrial pacing and simultaneous restoration of filling. Therefore, we designed this study to determine whether acute reduction in filling can induce new SWMA in the absence of ischemia. Institution of cardiopulmonary bypass was used as a clinical model of acute reduction in filling, and a beat-by-beat analysis of left ventricular contraction, filling, blood pressures, and electrocardiogram was performed when the drainage of blood to the cardiopulmonary bypass machine rapidly emptied the heart. Acute reduction in filling induced new SWMA in 4 of 38 study patients. All 4 patients had preexisting abnormalities of left ventricular contraction, but translocation of these preexisting SWMA did not explain the new SWMA, nor did myocardial ischemia. We conclude that acute reduction in left ventricular filling can cause new SWMA in the absence of ischemia. This finding limits the usefulness of new SWMA as a marker of ischemia in the presence of acute reduction in filling, such as that secondary to severe hypovolemia.

IMPLICATIONS

This study documented that acute reduction in cardiac filling can be associated with new systolic wall motion abnormalities detected by transesophageal echocardiography in the absence of documented myocardial ischemia. These findings indicate that segmental wall motion may not be a valid marker for ischemia in the setting of acute hypovolemia.

Relationship of regional wall motion abnormalities detected by biplane transesophageal echocardiography and electrocardiographic changes in patients undergoing coronary artery bypass graft surgery

BACKGROUND

It has been demonstrated that new regional wall motion abnormalities (RWMAs) are infrequently associated with electrocardiographic (ECG) ischemic changes during coronary artery bypass graft (CABG) surgery. The evaluation of apical or basal areas by biplane transesophageal echocardiography (TEE) may clarify the relationship between RWMA and ECG changes.

METHODS

Biplane TEE and ECG (leads II and V5) were continuously monitored in a total of 98 patients undergoing CABG surgery to determine the incidence and characteristics of RWMAs and to relate these findings to ECG changes.

RESULTS

Twenty-four new RWMAs were detected in 21 (21%) patients. Incidences of new RWMAs in each view were found to be as follows: 12 (50%) in short-axis view (SAV); 5 (21%) in long-axis view (LAV); and 7 (29%) in both views. Ten of the 24 new RWMA episodes (42%) corresponded to ECG ischemic changes. These new ECG changes were significantly more common when the new RWMAs appeared on both views (86%) as compared with the LAV alone (0%) (p < 0.01) or with SAV alone (33%). Moreover, in patients with a greater number of abnormal segments (> 3), new RWMAs were significantly (p < 0.05) associated with ECG changes.

CONCLUSION

Biplane TEE provides additional information about spatial distribution of new RWMAs. This study was the first to demonstrate that a clear relationship between TEE and ECG ischemia exists. When these new RWMAs exhibited a large spatial distribution, the frequency of ECG ischemic changes increased.

Anaesthesia for coronary artery surgery--a plea for a goal-directed approach

The purpose of the current literature review was to examine whether changes in current anaesthetic techniques are warranted for patients undergoing coronary artery surgery in light of recent information presented in the literature. The objectives of a cardiac anaesthetic technique are to maintain haemodynamic stability and myocardial oxygen balance, minimize the incidence and severity of ischaemic episodes, be aware of cardiopulmonary bypass-induced pharmacokinetic changes, and facilitate early tracheal extubation if appropriate. Many techniques have been utilized. Provided attention is paid to the details of managing myocardial oxygen supply and demand, none has emerged as superior in preventing intraoperative myocardial ischaemia. Silent myocardial ischaemia (i.e., ischaemia occurring in the absence of haemodynamic aberrations) is common throughout the perioperative period and may occur even in the presence of an appropriately used anaesthetic technique. The incidence and severity appear to be greatest in the postoperative period when the effects of anaesthesia are dissipating. The use of high-dose opioid anaesthesia may no longer be the most appropriate technique to facilitate the anaesthetic objectives. The role of pain management in altering the incidence of ischaemia requires further study. Increased waiting lists for cardiac surgery and ever-diminishing resources should prompt a re-evaluation of early extubation (i.e., within eight hours) as a method of improving utilization of scarce ICU resources. It is suggested that this should be possible with currently available agents to achieve the anaesthetic objectives. Future suggestions for research in this area are made.

What's new in monitoring the coronary surgery patient?

Monitoring has been extensively reviewed in most textbooks of cardiothoracic surgery and anaesthesia, particularly in the recent textbooks on monitoring edited by Carol L Lake 1 and Casey D Blitt 2 and in the Journal of Clinical Monitoring. Although monitoring properly includes both pre- and postoperative periods, this review will concentrate exclusively on the operative period. I will also concentrate on new approaches or information which relate to more traditional approaches to monitoring. The emphasis in this review will not be on what we can monitor, but rather on what we should monitor. In this regard, I will analyse accuracy and identify sources of error and try to answer the following questions. Does the device or parameter measure (monitor) what we want to know? Does it improve patient outcome and safety? Is it cost-effective? Unfortunately, data are not always available to answer all these questions at present, but hopefully the discussions will make us aware of what we do and do not know, and what we should look for in the near future.