Myocardial stunning: an overview

Dynamic progression of contractile and endothelial dysfunction and infarct extension in the late phase of reperfusion

BACKGROUND

Myocardial injury during early reperfusion (R) has been well documented. However, the extent and time course of myocardial injury during late R are still unclear. The purpose of this study was to determine the extent of regional contractile and endothelial dysfunction and myocardial blood flow (MBF) defect as well as extension of infarction in association with neutrophil (PMN) actions during R.

MATERIALS AND METHODS

A total of 29 dogs underwent a protocol of 1 h LAD ischemia followed by 6, 24, 48, and 72 h of R, respectively. Regional contractile function (sonomicrometry), MBF (colored microspheres), infarct size (triphenyltetrazolium chloride staining), and PMN localization (immunohistochemistry) were determined.

RESULTS

Percentage segmental shortening at 6, 24, 48, and 72 h of R was significantly blunted (-1.8 +/- 1.2,* - 0.37 +/- 0. 6,* 0.04 +/- 0.2,* and 5.9 +/- 1.2* vs baseline 17.7 +/- 0.8). MBF (ml/min/g) was attenuated at 24 (0.27 +/- 0.03*), 48 (0.46 +/- 0. 07*), and 72 h of R (0.48 +/- 0.06*) vs 6 h of R (0.65 +/- 0.06). Infarct size increased from 6 (27 +/- 2%) to 24 h of R (41 +/- 2%*) with no further increase at 48 and 72 h of R, consistent with a peak of creatine kinase activity. PMN adherence (mm(2) endothelium) to left anterior descending coronary artery (LAD) segments was increased after 6 h of R (63 +/- 3*) vs nonischemic left circumflex coronary artery (LCX) segments (42 +/- 2) with a peak at 48 h of R (111 +/- 5*). Endothelium-dependent vascular relaxation in the LAD was also blunted at 6, 24, and 48 h of R. Immunostaining revealed CD18-positive PMNs were mainly accumulated in intravascular space during 6 h of R with an increase in migration of PMNs seen at 24 h of R, consistent with a peak of myeloperoxidase release. Myeloperoxidase activity in a given area at risk sample was significantly correlated with infarct extension during the first 24 h of R.

CONCLUSIONS

These results provide pathologic evidence for myocardial injury during the extended R and a basis for exploration of interventions designed to limit myocardial injury after ischemia. (*P < 0.05 vs Baseline, 6 h of R and LCX segments.)

Assessment of ventricular function in critically ill patients: limitations of pulmonary artery catheterization. Institutions of the McSPI Research Group

OBJECTIVE

To determine the accuracy of conventional hemodynamic assessment using pulmonary artery catheter-derived data in critically ill patients.

DESIGN

Cohort study.

SETTING

Kaiser Permanente and Veterans Affairs Medical Centers.

PARTICIPANTS

Twenty-five consecutive patients who had undergone elective aortocoronary bypass surgery.

MEASUREMENTS AND MAIN RESULTS

In the intensive care unit, conventional assessment (CA) was performed hourly by clinicians using conventional (radial artery and pulmonary artery) hemodynamic measurements from which left ventricular (LV) function and intracardiac volume were estimated. Simultaneously, transesophageal echocardiography (TEE) data were recorded on videotape, blinded to the clinicians, and quantitatively analyzed off-line. TEE-determined LV function was classified as either normal (ejection fraction > or =40%) or abnormal (ejection fraction <40%) and intracardiac volume as normal (end-diastolic area = 8 to 22 cm2), low (end-diastolic area <8 cm2), or high (end-diastolic area >22 cm2).

CONCLUSION

Evaluable data included 130 of 150 (87%) observations of simultaneously collected CA and TEE data, averaging 5.6+/-4.4 observations per patient. The overall predictive probability for conventional clinical assessment of normal ventricular function was 98% (118/121), whereas for abnormal ventricular function it was 0% (0/9). For CA of volume, the overall predictive probabilities for hypovolemia, normovolemia, and hypervolemia were 50% (3/6), 60% (69/115), and 22% (2/9). Although conventional clinical assessment of normal LV function in the intensive care unit correlates well with echocardiographic assessment, both LV dysfunction and extremes of preload (hypovolemia or hypervolemia) are assessed poorly by clinicians using conventional clinical monitoring with pulmonary artery catheterization.

Persistent endocrine stress response in patients undergoing cardiac surgery

To investigate the endocrine stress response in patients undergoing major surgery with general anesthesia using a balanced technique with sufentanil, isoflurane and midazolam up to the second postoperative day, blood levels of cortisol, epinephrine, norepinephrine, prolactin and growth hormone were determined in 68 males for elective coronary artery bypass grafting (CABG) surgery. Intraoperatively, during extracorporeal circulation none of the measured parameters were significantly increased compared to preoperative values. The endocrine response of patients with perioperative epinephrine medication (n = 32) was not significant different to patients that did not receive exogenous epinephrine (n = 36). On the evening of the day of surgery, levels of cortisol (3 fold), epinephrine (4.7 fold), norepinephrine (1.7 fold) and growth hormone (16.5 fold) were significantly increased. Compared to preoperative values levels of cortisol (3.3 fold), growth hormone (5.5 fold) and norepinephrine (1.8 fold) remained elevated up to the evening of the second postoperative day. In conclusion, the endocrine stress response in patients undergoing CABG-surgery under general anesthesia with sufentanil, midazolam, isoflurane is intraoperatively prevented by anesthesia. Although hemodilution or hormone degradation might be responsible for the lack of an increase in endocrine parameters during CPB, this study indicates that a balanced technique with isoflurane, sufentanil and midazolam is more effective in blocking the endocrine stress response than previously described anesthetic techniques. In the early postoperative period, a sharp increase in cortisol, epinephrine, norepinephrine and growth hormone occurred suggesting that the predominant endocrine stress response begins in the intensive care unit with end of anesthesia. The postoperative elevated levels of cortisol, growth hormone and norepinephrine indicate a persisting stress-response for more than two days after surgical trauma.

Cardiovascular morbidity and CABG surgery--a perspective: epidemiology, costs, and potential therapeutic solutions

Although substantial advances have been made in the management of cardiovascular disease, it remains the leading cause of death on the United States and many other countries, due to the impact of aging and other changes in patient demographics. Since cardiovascular complications are usually associated with stress, it is not surprising that perioperative complications (cardiac death, myocardial infarction, heart failure) occur in at least 10% of patients undergoing coronary artery bypass graft surgery, with such complications consuming an additional $2 billion annually in health care resources. In addition, the limitations of the newly mandated cost-saving methods have and will continue to have an impact upon the delivery of health care to cardiovascular patients. However, research and clinical studies in this area hold the promise of appropriate and cost-effective therapeutic approaches.

A potential role for nitric oxide in myocardial stunning

Nitric oxide (NO) production by the human heart has been demonstrated in patients undergoing cardiac surgery. Similar to what has been described in other species, a basal production of NO by the human heart is seen (126 +/- 42 pmol/min per gram). Following reperfusion, at the end of the procedure, the level of NO production increases significantly reaching concentrations of 1430 +/- 330 pmol/min per gram. Increased activity for the enzyme NO synthase (NOS) (8.0 +/- 1.2 pmol/mg prebypass vs 26.4 +/- 4.8 pmol/mg postbypass) coincides with changes in NO production and occurs at a time when myocardial stunning is clinically detectable. The significance of these findings is discussed and suggest a role for NO in the pathophysiology of myocardial stunning.