Effect of dobutamine-induced myocardial ischemia on Doppler echocardiography after myocardial infarction

Intra-operative myocardial ischaemia cannot be detected by analysis of transmitral inflow patterns in patients undergoing off-pump coronary surgery

BACKGROUND AND OBJECTIVE

Transmitral inflow patterns have been used for detection of myocardial ischaemia. However, its diagnostic value has not been tested in anaesthetized and mechanically ventilated patients undergoing coronary artery bypass graft surgery.

METHODS

Transmitral inflow patterns were studied by transoesophageal Doppler echocardiography in 43 patients undergoing coronary artery bypass graft surgery without cardiopulmonary bypass after opening of the sternum (baseline) and during grafting of the left anterior descending artery. Peak early (E) and peak late (A) transmitral velocities and their ratio (E/A) were recorded. Myocardial ischaemia was defined by standard criteria using two-dimensional echocardiography and seven-lead electrocardiogram.

RESULTS

Thirty-one patients (64 +/- 8 yr, 9 women) fulfilled the predefined inclusion criteria for analysis. During distal revascularization, 16 patients showed myocardial ischaemia and 15 did not. The use of vasoactive drugs, haemodynamic findings and transmitral inflow patterns were similar in both groups at baseline and during grafting. In the ischaemic group, E was 67.1 +/- 13.9 cm s-1 at baseline and 69.5 +/- 23.2 cm s-1 during grafting, and the E/A ratios were 1.3 +/- 0.3 and 1.4 +/- 0.9, respectively. In the non-ischaemic group, E was 64.0 +/- 17.1 cm s-1 at baseline and 60.9 +/- 14.8 cm s-1 during grafting, and the E/A ratios were 1.4 +/- 0.7 and 1.2 +/- 0.3, respectively.

CONCLUSIONS

Analysis of Doppler findings of transmitral inflow patterns did not allow for detection of myocardial ischaemia during surgical revascularization of the myocardium.

MR flow mapping of dobutamine-induced changes in diastolic heart function

PURPOSE

To evaluate the ability of MR flow mapping to measure changes in left ventricular filling during beta-adrenergic stimulation.

MATERIALS AND METHODS

Mitral flow was measured in 10 healthy volunteers using conventional free breathing fast-field echo (FFE) with a spatial resolution of 2.7 x 2.2 mm and a temporal resolution of 22 msec. The sequence was repeated during dobutamine infusion (20 microg/kg/minute).

RESULTS

Stroke volume increased from a median of 99 mL (range: 68-142 mL) (Note: values as presented are medians and ranges, throughout) to 114 mL (87-180 mL) (P < 0.05). Both early (E) peak filling rate (554 mL/second [433-497 mL] to 651 mL/second [496-1096 mL/second]) (P < 0.05) and atrial (A) peak filling rate (238 mL/second [183-352 mL/second] to 341 mL/second [230-538 mL/second]) (P < 0.05) increased. These changes, together with the increase in E acceleration peak and A deceleration peak, were consistent with facilitated myocardial relaxation.

CONCLUSION

Conventional free breathing FFE has the ability to measure the effects of beta-adrenergic stimulation on left ventricular filling.

Short- and long-term prognostic value of cardiac troponin I and dobutamine echocardiography in patients with stabilized acute coronary syndromes

BACKGROUND

This study investigated the short- and long-term prognostic values of cardiac troponin I (cTnI) and dobutamine echocardiography (DE) in patients with acute coronary syndrome (ACS) who stabilized after medical treatment.

METHODS AND RESULTS

171 consecutive patients of ACS accepted blood sampling for cTnI at the emergency department and DE at 4.9+/-0.6 days after admission. The prognostic values of cTnI, DE, and combined cTnI and DE were separately investigated at follow up periods of 30 days, 1 year and 3 years for hard events (cardiac death and non-fatal myocardial infarction) and all spontaneous events. CTnI was elevated in 55 (32%) patients and DE was positive in 114 (67%) patients. Elevated cTnI with positive DE were found in 44 (26%) patients. Within 30 days, the combination of elevated cTnI and positive DE provided more accurate prognostic information than each test result alone, and was the only independent predictor for both hard (p=0.014) and all events (p=0.012). After 1 year, cTnI alone had no prognostic value. The combination of an elevated cTnI level and a positive DE only had a prognostic value for all events (p=0.015). However, DE was an independent predictor for both hard (p=0.006) and all events (p=0.002). Neither cTnI alone nor cTnI combined with DE had a significant 3-year prognostic value. However, DE maintained its prognostic value and was still an independent predictor after 3 years for both hard (p=0.024) and all events (p=0.004).

CONCLUSIONS

For patients with stabilized ACS, the diagnostic finding of elevated cTnI combined with a positive DE has a better short-term prognostic value than each test alone. However, DE alone has a better long-term prognostic value.

Dobutamine-induced hypotension is an independent predictor for mortality in patients with left ventricular dysfunction following myocardial infarction

Dobutamine echocardiography was performed on 297 patients after acute myocardial infarction to assess the prognostic value of dobutamine-induced hypotension in patients with left ventricular dysfunction. Patients were divided into two groups according to ejection fraction (group I, ejection fraction <0.45, n = 123; group II, ejection fraction > or =0.45, n = 174) and were followed for 20+/-8 months. Hypotension was defined as a decrease in systolic blood pressure > or =20 mm Hg, compared with baseline values. The incidence of hypotension was similar in groups I and II (23.6% vs. 18.4%, P = 0.28), and the hypotension was not related to positive dobutamine echocardiography. Univariate analysis showed that the development of hypotension was associated with a higher incidence of cardiac death in group I but not in group II. Multivariate analysis showed that dobutamine-induced hypotension was an independent predictor only for cardiac death in group I and was not related to any other cardiac events in either group. In conclusion, the development of hypotension during dobutamine stress can identify a subgroup with poor ventricular functional reserve and at high risk for cardiac death among patients complicated with left ventricular dysfunction.

Diagnostic value of dobutamine echocardiography in patients with angina-like symptoms preceding syncope

Dobutamine echocardiography was performed in 55 patients with syncope which was clinically suspected to be angina-related. We evaluated the value of using a single test, dobutamine echocardiography, in differentiating real ischemia-related from vasovagal syncope which was diagnosed by a tilt test. During testing, supraventricular arrhythmia was provoked in four (7.2%) patients. Dobutamine echocardiography identified all of six (10.9%) patients (sensitivity 100%), who were found with significant coronary stenosis by coronary angiograms. The etiology of syncope in the remaining 45 patients was investigated further by tilt testing, the findings of hypotension and bradycardia during which were compared head to head with those of dobutamine echocardiography. Tilt testing diagnosed vasovagal syncope in 31 patients, in whom only 19 (61.3%) patients developed vasovagal reflex during dobutamine echocardiography. Conclusively, dobutamine echocardiography had a high sensitivity in identifying syncope related to myocardial ischemia in patients with coronary stenosis, but a low sensitivity (61.3%), high specificity (90.5%) and high positive predictive value (81.8%) in detecting the syncope patients with angina caused by vasovagal effect.

Prognostic value of dobutamine echocardiography in patients after Q-wave or non-Q-wave acute myocardial infarction

We investigated the role of dobutamine echocardiography in predicting future spontaneous events in patients with Q-wave or non-Q-wave first acute myocardial infarction (AMI). DE was performed in 168 patients with a Q-wave AMI and 105 patients with a non-Q-wave AMI. Patients were observed for hard events (cardiac death and nonfatal reinfarction) and all spontaneous events (hard events and unstable angina). When compared to patients with a Q-wave AMI, patients with non-Q-wave AMI had a higher rate of positive dobutamine echocardiographic results (51.8% vs 80.0%, p <0.0001), greater changes in wall motion score index (WMSI) (0.31+/-0.17 vs 0.42+/-0.23, p = 0.001), and more remote zone ischemia (27.9% vs 43.8%, p = 0.0072). Patients with non-Q-wave infarct had a higher all-event rate, but a similar hard-event rate. In patients with a positive dobutamine echocardiogram (DE), the rate of hard or all events was similar, regardless of different infarct patterns. Patients with a negative DE had a higher event-free survival rate for all events in both Q-wave (85.2% vs 60.9%, p <0.0001) and non-Q-wave (76.2% vs 52.4%, p = 0.0083) groups. By stepwise analysis in the Q-wave group, the most important predictors were peak stress WMSI and diabetes for hard events, and a positive DE and baseline WMSI for all events. However, in the non-Q-wave group, the strongest predictors were dobutamine time for hard events and positive DE for all events. We conclude that a positive DE is a powerful predictor of future spontaneous events in patients after either a Q-wave or non-Q-wave AMI. However, for hard events, high-risk patients with different infarct patterns were recognized with variable efficiency by different dobutamine echocardiographic variables.