Clinical and angiographic correlates of dobutamine-induced wall motion patterns after myocardial infarction

Right ventricular pressure dynamics and stress echocardiography in pharmacological and exercise stress testing

REASONS FOR PERFORMING STUDY

There is interest in using pharmacological stress testing (PST) as a substitute for exercise stress testing (EST) to evaluate cardiac function in horses.

OBJECTIVES

To compare the effect of PST and EST on right ventricular pressure dynamics and stress echocardiography.

METHODS

Five horses completed a PST and EST in a randomised crossover design. High fidelity pressure transducers were placed in the right ventricle. Continuous pressure signals were digitally collected and stored, and dP/dtmax, dP/dtmin and tau calculated from these measurements. ECGs were recorded continuously for 20 h. Echocardiography was performed prior to EST and PST, during and after PST, and immediately post EST. Plasma cardiac troponin I concentrations were measured pre- and 3-4 h post stress testing. For PST, 5 microg/kg bwt glycopyrrolate i.v. followed after 10 min by 5 microg/kg bwt/min dobutamine infusion over 10 min was given. EST consisted of a 2 min gallop at 110% speed required to elicit VO2max.

RESULTS

Both EST and PST resulted in a significant increase in right-ventricular dP/dtmax and dP/dtmin over baseline (P<0.05) and a significant decrease in tau compared with baseline (P<0.05). EST dP/dtmax and dP/dtmin were significantly greater than PST dP/dtmax and dP/dtmin (P<0.05) and EST tau was significantly less than PST tau (P<0.05). Two minutes post EST and 5 min post PST dP/dtmax were not significantly different, but were significantly less than end-EST and during PST. Tau was also not significantly different between post EST and post PST, but was significantly decreased end-EST compared with during PST. FS were not significantly different between PST and post EST, but during PST and post EST all FS were significantly higher than baseline. Cardiac troponin I concentrations were significantly elevated post PST and were greater than post EST. The clinical relevance of this is unknown.

CONCLUSIONS

PST had a similar, although less marked effect on the cardiac parameters related to right-ventricular pressure dynamics and a similar effect on echocardiography as exercise stress testing.

POTENTIAL RELEVANCE

PST deserves further evaluation in normal horses and those with cardiac disease, and may be complementary to EST to better identify exercise-induced cardiac dysfunction.

Assessment of myocardial viability: comparison of echocardiography versus cardiac magnetic resonance imaging in the current era

Detecting viable myocardium, whether hibernating or stunned, is of clinical significance in patients with coronary artery disease and left ventricular dysfunction. Echocardiographic assessments of myocardial thickening and endocardial excursion during dobutamine infusion provide a highly specific marker for myocardial viability, but with relatively less sensitivity. The additional modalities of myocardial contrast echocardiography and tissue Doppler have recently been proposed to provide further, quantitative measures of myocardial viability assessment. Cardiac magnetic resonance (CMR) has become popular for the assessment of myocardial viability as it can assess cardiac function, volumes, myocardial scar, and perfusion with high-spatial resolution. Both 'delayed enhancement' CMR and dobutamine stress CMR have important roles in the assessment of patients with ischaemic cardiomyopathy. This article reviews the recent advances in both echocardiography and CMR for the clinical assessment of myocardial viability. It attempts to provide a pragmatic approach toward the patient-specific assessment of this important clinical problem.

Predictive Value of Biphasic Response During Dipyridamole Echocardiography Test in the Low-risk Group of Patients After Acute Myocardial Infarction

To investigate whether biphasic response during dipyridamole echocardiography test (DET), which represents viable but potentially ischemic myocardium in the infarcted region, affects prognosis of patients after uncomplicated acute myocardial infarction, we performed high-dose DET in 80 consecutive patients younger than 65 years with first acute myocardial infarction and preserved left ventricular function. Patients were followed up for 27 +/- 12 months for new coronary events. According to DET results all patients were classified into 4 groups: group 1 consisted of 20 patients with biphasic response; group 2 included 14 patients with sustained improvement in regional contractility; group 3 consisted of 24 patients showing no change in contractility; and group 4 included 22 patients with worsening response. Cumulative survival free of total coronary events was significantly lower in group 1 patients compared with all other groups (P < .05). By multivariate Cox analysis biphasic response was the strongest independent predictor of stable angina pectoris (odds ratio = 12.1, P = .0002), followed by hyperlipoproteinemia (odds ratio = 5.9, P = .006). On the other hand, development of acute coronary syndromes could not have been predicted by actual clinical or DET parameters.

Infarct-related artery occlusion, tissue markers of ischaemia, and increased apoptosis in the peri-infarct viable myocardium

AIMS

Unfavourable cardiac remodelling often complicates acute myocardial infarction (AMI) as a result of increased cardiomyocyte apoptosis. It is currently unclear whether ongoing or recurrent ischaemia is an independent determinant for increased apoptosis in peri-infarct viable myocardium.

METHODS AND RESULTS

In order to assess the link between infarct-related artery (IRA) occlusion, ischaemia, and apoptosis, 30 subjects dying 7-120 days after AMI (16 with IRA occlusion and 14 with patent IRA) and five control subjects were selected at autopsy. Cardiomyocytes were defined as apoptotic if co-expressing TUNEL and activated caspase-3. Expression of both hypoxia-inducible factor-1 and cyclo-oxygenase-2 was assessed in the peri-infarct myocardium and considered as tissue markers of ischaemia. Evidence of ischaemia was significantly more frequent in cases with IRA occlusion (53%) than in cases with patent IRA (15%) or control hearts (0%, P=0.026). The finding of IRA occlusion and markers of ischaemia identified cases with higher apoptotic rates (ARs) in the peri-infarct viable myocardium [12.2% (8.2-14.0), P<0.001 vs. others], whereas IRA occlusion without ischaemia was associated with lower AR, not significantly different from patent IRA [3.0% (1.0-7.9) vs. 2.2% (1.0-5.8), respectively, P=0.42]

CONCLUSION

Ischaemia in the peri-infarct viable myocardium is present in over 50% of subjects dying late after AMI with IRA occlusion, and it is associated with increased apoptosis. Relief of ischaemia after AMI may prove of benefit in preventing apoptosis and its consequences.

Ultrasound imaging versus morphopathology in cardiovascular diseases. Coronary collateral circulation and atherosclerotic plaque

This review article is aimed at comparing the results of histopathological and clinical imaging studies to assess coronary collateral circulation in humans. The role of collaterals, as emerging from morphological studies in both normal and atherosclerotic coronary vessels, is described; in addition, present role and future perpectives of echocardiographic techniques in assessing collateral circulation are briefly summarized.

Value of echocardiography in predicting future cardiac events after acute myocardial infarction

Short- and long-term survival after acute myocardial infarction mainly depends on three factors: the amount of myocardium that had become necrotic, the area of myocardium at further risk of becoming necrotic, and the patency of the infarct-related artery. Echocardiography is a low-cost, safe, bedside, repeatable tool, particularly useful for prognostic stratification after myocardial injury. Two-dimensional echocardiography analyzes left ventricular function, the most powerful predictor of survival immediately after acute myocardial infarction. Myocardial contrast echocardiography measures the infarct size and detects viable myocardium. Stress echocardiography stratifies patients with viable myocardium and/or multivessel coronary artery disease who need further diagnostic and therapeutic interventions. Transthoracic coronary Doppler ultrasonography assesses effective recanalization and coronary flow reserve of the left anterior descending coronary artery. Further technologic advances are needed to allow direct noninvasive measurement of flow by transthoracic Doppler ultrasonography in other coronary arteries.

The non-invasive assessment of hibernating myocardium in ischaemic cardiomyopathy--a myriad of techniques

Heart failure is placing an ever-increasing burden on society. Many subjects with heart failure and underlying coronary artery disease have a significant amount of akinetic but viable myocardium that is able to contract should myocardial perfusion improve (hibernating myocardium). Non-randomised studies have shown prognostic benefit in subjects with hibernating myocardium undergoing revascularisation. Several non-invasive techniques have been developed to assess the presence or absence of hibernating myocardium. This review will examine the epidemiology and underlying pathogenesis of hibernating myocardium; evaluate the non-invasive techniques for diagnosing hibernating myocardium, and look at therapeutic intervention in subjects with hibernating myocardium.

Observation of the ischemic cascade in humans using contrast echocardiography during dobutamine stress

Experimental studies have postulated the ischemic cascade and the present study was designed to elucidate whether it can be observed in the clinical setting. Fifty-three patients suspected of having coronary artery disease were studied. Myocardial perfusion abnormalities (MPA) and wall motion abnormalities (WMA) were assessed simultaneously by infusion of Levovist during dobutamine stress echocardiography. Time - intensity data of myocardial opacification were fitted for Y=A (1-e(-)(beta) (t)) from which the rate of increase (beta) of intensity were derived both at rest and during stress. Wall motion was also given a score. Bright opacification was observed in 50 patients: 25 showed significant stenosis (>50%) in the left anterior descending artery (group II) on coronary angiography and 25 did not (group I). Significant differences were found in the beta ratio (stress/rest) between the 2 groups at a low-dose (2.0+/-0.3 vs 1.5+/-0.5, p<0.05) and at a high-dose of dobutamine (2.7+/-1.0 vs 1.1+/-0.5, p<0.001), whereas the wall motion score differed only at a high-dose. Of the 25 patients in group II, MPA preceded WMA in 12, both occurred at the same stage in 12, and neither MPA nor WMA was seen in 1. These data prove the ischemic cascade clinically, using contrast echocardiography, by demonstrating that MPA precede WMA during dobutamine stress in patients with coronary stenosis.