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

The ischaemic constellation: an alternative to the ischaemic cascade-implications for the validation of new ischaemic tests

The ischaemic cascade is the concept that progressive myocardial oxygen supply-demand mismatch causes a consistent sequence of events, starting with metabolic alterations and followed sequentially by myocardial perfusion abnormalities, wall motion abnormalities, ECG changes, and angina. This concept would suggest that investigations that detect expressions of ischaemia earlier in the cascade should be more sensitive tests of ischaemia than those that detect expressions appearing later in the cascade. However, careful review of the studies on which the ischaemic cascade is based suggests that the ischaemic cascade concept may be less well supported by the literature than assumed. In this review we explore this, discuss an alternative method for conceptualising ischaemia, and discuss the potential implications of this new approach to clinical studies and clinical practice.

Quantitative myocardial contrast echocardiography during pharmacological stress for diagnosis of coronary artery disease: a systematic review and meta-analysis of diagnostic accuracy studies

AIMS

We conducted a meta-analysis to evaluate the accuracy of quantitative stress myocardial contrast echocardiography (MCE) in coronary artery disease (CAD).

METHODS AND RESULTS

Database search was performed through January 2008. We included studies evaluating accuracy of quantitative stress MCE for detection of CAD compared with coronary angiography or single-photon emission computed tomography (SPECT) and measuring reserve parameters of A, beta, and Abeta. Data from studies were verified and supplemented by the authors of each study. Using random effects meta-analysis, we estimated weighted mean difference (WMD), likelihood ratios (LRs), diagnostic odds ratios (DORs), and summary area under curve (AUC), all with 95% confidence interval (CI). Of 1443 studies, 13 including 627 patients (age range, 38-75 years) and comparing MCE with angiography (n = 10), SPECT (n = 1), or both (n = 2) were eligible. WMD (95% CI) were significantly less in CAD group than no-CAD group: 0.12 (0.06-0.18) (P < 0.001), 1.38 (1.28-1.52) (P < 0.001), and 1.47 (1.18-1.76) (P < 0.001) for A, beta, and Abeta reserves, respectively. Pooled LRs for positive test were 1.33 (1.13-1.57), 3.76 (2.43-5.80), and 3.64 (2.87-4.78) and LRs for negative test were 0.68 (0.55-0.83), 0.30 (0.24-0.38), and 0.27 (0.22-0.34) for A, beta, and Abeta reserves, respectively. Pooled DORs were 2.09 (1.42-3.07), 15.11 (7.90-28.91), and 14.73 (9.61-22.57) and AUCs were 0.637 (0.594-0.677), 0.851 (0.828-0.872), and 0.859 (0.842-0.750) for A, beta, and Abeta reserves, respectively.

CONCLUSION

Evidence supports the use of quantitative MCE as a non-invasive test for detection of CAD. Standardizing MCE quantification analysis and adherence to reporting standards for diagnostic tests could enhance the quality of evidence in this field.

Real-time myocardial contrast stress echocardiography using bolus application

In myocardial contrast echocardiography (MCE), power modulation technique may quantify myocardial perfusion in real-time. However, constant infusion of the contrast agent (CA) complicates handling. This pilot study sought for the clinical feasibility of quantitative MCE by a CA bolus application during Adenosine stress echocardiography to diagnose coronary artery disease (CAD). Twenty-four consecutive patients (pts) with contemporary coronary angiography underwent rest and maximum Adenosine stress. Signal intensity could be calculated in 316/348 left ventricular (LV) segments (91%) (18-segment model). At rest, gamma-variate (alpha) as well as saturation function (beta) was not significantly different in healthy men (n = 268) as well as CAD pts (n = 48) (alpha: 0.34 s(-1) versus 0.40 s(-1), n.s.; beta: 0.31 s(-1) versus 0.35 s(-1), n.s.). During Adenosine infusion both values increased in healthy men (alpha: 0.34 +/- 0.37 s(-1) versus 0.44 +/- 0.45 s(-1), p < 0.05; beta: 0.31 +/- 0.33 s(-1) versus 0.40 +/- 0.40 s(-1), p < 0.01), but not in CAD (alpha: 0.40 +/- 0.35 s(-1) versus 0.29 +/- 0.29 s(-1), n.s.; beta: 0.35 +/- 0.32 s(-1) versus 0.27 +/- 0.30 s(-1), n.s.). Sensitivity of alpha/beta reserve <or=1 was 65%/67% (specificity 66%/67%) and improved to 88% in both if also wall motion analysis was considered (specificity 59%/65%). A very high negative predictive value of 96%/97% favours the method for excluding CAD. Bolus administration of CA is feasible in quantitative real-time MCE. However, additional consideration of wall motion analysis is required for reasonable sensitivity. Very high negative predictive values favour the potential of the method in excluding the diagnosis. Further need of research work may be encouraged by those findings.

Usefulness of a novel ultrasound transducer for continuous monitoring treadmill exercise echocardiography to assess coronary artery disease

BACKGROUND

The feasibility of a novel ultrasound probe, which can be attached to the left ventricular (LV) apex chest wall and allows free rotation around its long axis direction for the continuous monitoring of LV wall motion, was tested.

METHODS AND RESULTS

There were 36 subjects who had coronary artery disease (CAD). By attaching a novel ultrasound probe to the chest wall, the LV apical views were recorded during treadmill exercise stress echocardiography (Echo). The continuous monitoring of LV wall motion was satisfactorily feasible in 30 of 36 patients. The visualization rate of the overall LV segments was higher at rest (90%) compared to that during peak exercise (77%). The segments were better visualized in apical portions (90-100%) than in mid (77-96%) or basal portions (68-87%). The sensitivity, specificity, and accuracy for detecting CAD were 61, 100 and 77%, respectively. The wall motion score index 3 and 6 min after exercise decreased significantly compared to those at peak exercise. The number of segments with dyssynergy was highest at the peak exercise. Ischemic ST-T depression on electrocardiography was observed only at peak stress periods.

CONCLUSIONS

Continuous monitoring treadmill exercise Echo using a novel ultrasound probe seems feasible for the non-invasive and physiological assessment of CAD.

Noninvasive detection of coronary allograft vasculopathy by myocardial contrast echocardiography

BACKGROUND

Noninvasive detection of coronary allograft vasculopathy is still challenging. To determine the accuracy of myocardial contrast echocardiography (MCE) in detecting coronary allograft vasculopathy after heart transplantation, we studied 35 asymptomatic patients (30 men, aged 46 +/- 12.7 years) with normal left ventricular function.

METHODS

Patients underwent MCE with continuous contrast (perfluorocarbon-exposed sonicated dextrose albumin) administration. Images were obtained at baseline and during peak dobutamine (up to 40 mg/kg/min) with intermittent harmonic imaging. Areas failing to increase contrast enhancement during peak stress were regarded as abnormal. Coronary artery obstructions greater than 50% at angiography were considered significant.

RESULTS

Seven out of 10 patients with coronary artery disease had a positive MCE and one patient with a positive MCE had no angiographically detected disease (sensitivity = 70%, specificity = 96%, accuracy = 88.6%). Agreement between the vascular territory and perfusion defects was good for the left anterior descending coronary artery (kappa = 0.56), but not for other arteries. Although 5 patients had multivessel disease, multiple perfusion defects were detected in only one patient.

CONCLUSION

MCE showed good accuracy in detecting the presence of coronary allograft vasculopathy after heart transplantation; however, it failed to identify the extent of the disease.

Relation of Myocardial Blood Volume to Left Ventricular Function and Future Cardiac Events in Patients With Idiopathic Dilated Cardiomyopathy

BACKGROUND

The hypothesis that myocardial blood volume is associated with left ventricular (LV) dysfunction and future cardiovascular events in patients with idiopathic dilated cardiomyopathy (IDC) was tested using intravenous myocardial contrast echocardiography (MCE).

METHODS AND RESULTS

Thirty-five patients with IDC and 10 age-matched healthy control subjects were enrolled. Using MCE, background-subtracted and peak myocardial contrast intensity (calibrated PMCI) were calculated as measures of myocardial blood volume. LV ejection fraction (LVEF) was calculated using the modified Simpson method. Patients with IDC were stratified into 2 groups according to the median value of the calibrated PMCI [high value group (n=17): calibrated PMCI > or = -22.7 dB, low value group (n=18): calibrated PMCI < -22.7 dB]. The calibrated PMCI was markedly reduced in patients with IDC compared with the control subjects (p=0.0025) and closely related to LVEF (r=0.688, p<0.0001). In the multivariate model, calibrated PMCI was the independent variable that predicted cardiac events in patients with IDC. According to the Kaplan-Meier analysis, cardiac event-free rates were significantly lower in the low-value group than in the high-value group (p<0.01).

CONCLUSIONS

Myocardial blood volume is closely related to LV dysfunction and future cardiac events in patients with IDC.