Estimation of myocardial performance in CABG patients

Assessment of Left Ventricular Dimensions by Transoesophageal Echocardiography in Patients During Coronary Artery Bypass Surgery

OBJECTIVE

Normative values of left ventricular (LV) end-diastolic area and diameter (EDA and EDD) for intraoperative transoesophageal echocardiography (TEE) have not been established. We aimed to define the ranges of LV EDA and EDD for intraoperative TEE examinations in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

A MEDLINE search for studies reporting LV EDA and EDD in CABG patients was performed. Individual-level dataset from 333 anaesthetised and mechanically ventilated patients with preserved LV function (study population) were received from 8 studies. EDA and calculated EDD values in the study population were compared with summary mean EDD values obtained by transthoracic echocardiography (TTE) in 2 studies of 500 awake patients with coronary artery disease (CAD). Further, the influence of prespecified factors on EDD was evaluated through a multivariate regression model.

RESULTS

LV EDA and EDD values measured by TEE in anaesthetised CABG patients were 16.7±4.7 cm2 and 4.6±0.6 cm, respectively. EDD values measured by TEE in anaesthetised patients were 10% to 13% less those measured by TTE in 2 studies of awake patients (p<0.001). Body surface area, age and fractional area change but not sex were factors that affected LV EDD.

CONCLUSION

LV EDD values measured by intraoperative TEE in anaesthetised and mechanically ventilated CABG patients were 10% to 13% less than those measured by TTE in awake CAD patients. This finding indicates that independent normative values specific for intraoperative TEE should be established for guiding intraoperative clinical decisions.

Interval Changes in Myocardial Performance Index Predict Outcome in Severe Sepsis

OBJECTIVES

Septic cardiomyopathy is a well-described consequence of septic shock and is associated with increased sepsis-related mortality. The myocardial performance index (MPI), a parameter derived from echocardiographic tissue Doppler measurements, allows for a more sensitive assessment of global cardiac function than do traditional metrics for cardiac function. The authors hypothesized that changes in left ventricular MPI in patients with severe sepsis would be associated with a higher 90-day mortality.

DESIGN

Prospective, observational study.

SETTING

Intensive care units of a tertiary medical center.

PARTICIPANTS

The study comprised 47 patients admitted with new diagnoses of severe sepsis or septic shock.

INTERVENTIONS

All patients underwent transthoracic echocardiograms with assessment of MPI at enrollment and 24 hours later. Hemodynamic data and information on sepsis-related mortality were collected. In the primary analysis, the association between change in MPI from enrollment to 24 hours and sepsis-related 90-day mortality was assessed.

MEASUREMENTS AND MAIN RESULTS

Of the 47 patients enrolled, 30 demonstrated an improvement in MPI from 0 to 24 hours ("improved" group), and MPI worsened in the remaining 17 patients ("worsened" group). Despite no significant differences in ejection fraction or severity of illness, the median MPI at enrollment in the "improved" group was higher than baseline values in the "worsened" group (p = 0.005). A worsening MPI over the 24-hour study interval was associated with increased mortality at 90 days (p = 0.04), which remained significant (hazard ratio 3.72; 95% confidence interval 1.12-12.41; p = 0.03) after adjusting for severity of illness (Acute Physiology and Chronic Health Evaluation II score), intravenous fluids, and vasopressor use.

CONCLUSIONS

In patients admitted to the intensive care unit with a diagnosis of severe sepsis or septic shock, a worsening MPI during the first 24 hours after intensive care unit admission was associated with higher 90-day mortality.

The Failing Heart Under Stress: Echocardiography is an Essential Monitoring Tool in the Intensive Care Unit

Echocardiography has been evolving to play a pivotal role in hemodynamic management, both intraoperatively and at the bedside. A full assessment of hemodynamics necessitates the use of all of the options available on modern echocardiographs. This introductory review provides insight into three important issues of hemodynamic monitoring by echocardiography: evaluation of preloading conditions, assessment of systolic function, and contractility and estimation of afterload. Mastering these three features will help in a minimally invasive approach of hemodynamic instability.

Mild carbon monoxide poisoning impairs left ventricular diastolic function

Rationale:

Carbon monoxide (CO) poisoning is associated with direct cardiovascular toxicity. In mild CO poisoning in which cardiovascular life support is not required, the effects of CO on left and right ventricular functions are unknown in patients without cardiac failure.

Objectives:

Echocardiography was used to determine whether or not mild CO poisoning impairs ventricular function. Twenty otherwise healthy patients with CO poisoning and 20 age- and gender-matched controls were studied. Echocardiographic examinations were performed at the time of admission and 1 week after poisoning.

Results:

The impairment observed in the left and right ventricular diastolic function at the time of admission was greater than the impairment 1 week after poisoning. Mild CO poisoning did not have a significant effect on systolic function. Carboxyhemoglobin levels were positively correlated with left ventricular diastolic dysfunction, whereas the levels were not correlated with right ventricular diastolic function.

Conclusions:

In CO intoxication, the development of left and right ventricular diastolic dysfunction precedes systolic abnormality. Patients with mild CO poisoning do not manifest cardiovascular symptoms; however, it should be borne in mind that most of these patients have myocardial involvement.

Beat-to-beat change in "myocardial performance index" related to load

BACKGROUND

This study was designed to assess the relationship of the "myocardial performance index" (MPI) to the beat-by-beat change in pre-load with static or unchanged contractile status.

METHODS

Eight anesthetized juvenile pigs were studied using direct measurement of the left ventricular pressure and volume. Transient inflation of a vena cava balloon catheter produced controlled pre-load alterations. Consecutive beats were analyzed, grouped for first, second, third, etc. during the pre-load alteration, and evaluated for the change in MPI during the same contractile status with a controlled pre-load alteration. Two pharmacologic inotropic interventions were also included to generate several myocardial conditions in each animal.

RESULTS

MPI demonstrated a strong linear relationship to the pre-load and after-load. MPI increased progressively during decreasing end-diastolic volume, mostly related to changes in ejection time. MPI was observed at the same level for three different myocardial function conditions (all eight animals), with a different relationship between MPI and pre-load noted for each observation.

CONCLUSIONS

MPI is strongly load dependent, and can vary widely in value for the same contractile status if the load is varied. The use of this index in critically ill patients should be limited in this respect. Further work is needed to establish the relationship of MPI to load and contractile status.

Correlation of the Myocardial Performance Index with Conventional Echocardiographic Indices of Systolic and Diastolic Function: A Study in Cardiac Surgical Patients

BACKGROUND

The aim of this investigation was to compare the myocardial performance index (MPI), a Doppler-derived parameter of global ventricular function, with standard echocardiographic measures of systolic and diastolic function in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

Complete two-dimensional and Doppler examinations were performed on 46 CABG patients after induction of anesthesia (baseline), 15 minutes postcardiopulmonary bypass (CPB), and at the end of the surgical procedure.

RESULTS

A strong inverse correlation between MPI and both fractional area change (adjusted r(2)= 0.588-0.802) and ejection fraction (adjusted r(2)= 0.576-0.656, both P < 0.001) of the left ventricle was observed throughout the intraoperative period. Following CPB, a weaker correlation was observed between MPI and overall diastolic heart function classification (adjusted r(2)= 0.224-0.268, P <0.001). Weak, though statistically significant, correlations were observed between MPI and deceleration time (P < 0.05), peak atrial reversal (AR) wave velocity (P < or =0.002), and duration of the AR wave (P < 0.05).

CONCLUSION

Our data suggest that the MPI correlates well with standard echocardiographic measures of systolic function and modestly well with overall diastolic heart function classification. The MPI may be a useful, complementary marker of global left ventricular function in patients undergoing CABG surgery.

Opioids and Cardioprotection: The Impact of Morphine and Fentanyl on Recovery of Ventricular Function After Cardiopulmonary Bypass

OBJECTIVES

Experimental studies have shown that opioids protect the myocardium from ischemic injury and that opioid cardioprotection is enhanced by the coadministration of volatile anesthetics. Previous data suggest that morphine produces a more potent cardioprotective effect than fentanyl. The present study investigated the effect of the choice of intraoperative opioid (morphine or fentanyl) on recovery of myocardial function after coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PARTICIPANTS

Forty-six patients undergoing CABG surgery.

INTERVENTIONS

Patients were randomly assigned to receive either morphine (40 mg) or fentanyl (1,000 mug) before cardiopulmonary bypass (CPB). Global cardiac function was assessed intraoperatively using the myocardial performance index (MPI), which combines echocardiographic parameters of both systolic and diastolic function.

MEASUREMENTS AND MAIN RESULTS

The MPI (median [range]) was increased after CPB in the fentanyl group, indicating a significant worsening of global left ventricular function (0.43 [0.28-0.54] baseline; 0.49 [0.32-0.64] 15 minutes post-CPB; 0.51 [0.36-0.63] end of operation; p < 0.05 post-CPB compared with baseline). The MPI improved in the morphine group after CPB (0.44 [0.32-0.64] baseline; 0.36 [0.24-0.45] 15 minutes post-CPB; 0.34 [0.20-0.46] end of operation; p < 0.05 post-CPB compared with baseline and the fentanyl group).

CONCLUSIONS

In patients undergoing CPB, global ventricular function is enhanced by the administration of morphine prior to the ischemic insult of cardioplegic arrest.