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Myocardium selective densitometric perfusion assessment after acute myocardial infarction☆

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Abstract

Background

Myocardial perfusion is an important prognostic factor after recanalisation in acute myocardial infarction patients. We present a computerized, densitometric measurement method to assess myocardial perfusion on phase-matched digitally subtracted coronary angiograms.

Methods and materials

Quantitative myocardial perfusion was assessed by the Gmax/Tmax parameter of the time–density curves (TDCs) in infarct-related myocardial regions on X-ray coronary angiograms. Arteries were masked out from regions of measurement. This novel method has been compared with enzymatic infarct size, ST-segment resolution, and ejection fraction after successful revascularization of 62 patients with acute myocardial infarction.

Results

Significant correlations were found between Gmax/Tmax and enzymatic infarct size (R=−0.445, P<.001), ST-segment resolution (R=0.364, P=.004), and ejection fraction (R=0.278, P=.029). Bland and Altman plot of Gmax/Tmax reveals good interobserver agreement.

Conclusions

Gmax/Tmax of the TDC measured in the infarct-related myocardial area is a reliable parameter to assess clinical indicators of myocardial reperfusion. Therefore, results suggest that it could be used to immediately assess the success of recanalisation at the tissue perfusion level during coronary intervention, and as an objective end point in clinical trials of new interventional devices and drugs.

Introduction

The primary objective of treatment for acute myocardial infarction (AMI) is to restore normal blood flow in the epicardial infarct-related artery and to obtain reperfusion of the myocardium at risk. Assessment of myocardial perfusion on coronary angiograms is performed by visual estimation in the current clinical practice. Two visual grading scales proved to be informative in assessing the viability of the infarct-related myocardium: Myocardial Blush Grade [1] and TIMI Myocardial Perfusion Grade [2]. Both grades have four levels: 0 and 1 representing no or minimal contrast signal in the infarct related myocardium and 2 and 3 representing impaired and normal states. The interobserver and intraobserver variabilities associated with subjective angiographic assessments are limitations of these visual grades.

Methods for computerized videodensitometric analysis of digital subtraction coronary angiograms have been reported to be under study for a long time both in animal models and in human subjects. The primary goal of these studies was to develop an operator-independent and quantitative way of myocardial perfusion assessment based on X-ray coronary angiograms, which is the only imaging modality widely available during coronary interventions. Pijls et al. [3] demonstrated in a canine model that mean transit time calculated by videodensitometry can be used to assess myocardial perfusion. Haude et al. [4] also proved an excellent correlation of a similar method with myocardial perfusion using colored microspheres. More recent reports proved that even volumetric blood flow measurements are feasible by densitometry [5], [6].

Despite the promising results, none of these methods has yet been shifted to the clinical practice or became a standard end point of clinical trials in place of the four-graded visual assessment. Clinical environment, especially in case of AMI patients, does not allow the direct application of methods developed for experimental studies. Korosoglou et al. [7] recently published the results of a study of AMI patients proving that the computerized method for myocardial perfusion assessment is clinically feasible. Their results suggest that this low-cost measurement provides incremental prognostic value compared to the semi-quantitative visual assessment. However, the software used is not yet available and also has other limitations [8], e.g., coronary arteries should be excluded from the region of measurement, which severely limits the myocardial area where the method is applicable.

The objective of the present study was to evaluate regional myocardial perfusion assessed by a novel computerized videodensitometric method, and its relation to electrocardiographic, echocardiographic, and enzymatic indicators of myocardial damage in AMI patients after coronary intervention.

Section snippets

Study populations

The study comprised 62 patients with AMI, who underwent primary percutaneous coronary intervention (PCI) at the Invasive Cardiology Division of the University of Szeged. Patients with the following inclusion criteria were enrolled into the present study: (1) acute ST-elevation on 12-lead ECG; (2) pain-to-balloon time <12 h; (3) total occlusion of the proximal segment in one of the three main coronary arteries; and (4) ability of the patient to cooperate. Demographic and clinical data of the

Results

All patients underwent a successful recanalisation of the occluded vessel and achieved <50% residual stenosis within 12 h from the onset of symptoms. Plotting the Gmax/Tmax values on Bland–Altman plot and scatter diagram obtained by two independent observers reveals a reliable interobserver agreement (Fig. 2) of our method.

Enzymatic infarct size as expressed by sum of CK release had a significant negative correlation (R=−0.445, P<.001) with Gmax/Tmax. Scatter plot and regression line along with

Discussion

Results of the present study show that the demonstrated computerized videodensitometric method for regional myocardial perfusion assessment can be used in clinical circumstances to get immediate information on the viability and functionality of the revascularised myocardium. Moreover, measurements correlate with clinical indicators of myocardial damage suggesting it as an end point for studies on the success of recanalisation in AMI.

There is an abundance of evidence from several techniques,

References (16)

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This study was partially supported by the Regional Cooperative Research Center of Life and Material Sciences of the University of Szeged together with industrial partner General Electric Healthcare Hungary. Dr. Tamás Ungi holds a Ph.D. scholarship from the University of Szeged.

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