Quantitative evaluation of collateral circulation in patients with previous myocardial infarction: relation to myocardial ischemia, angiographic appearance and functional improvement of myocardium

The collateral circulation of the heart in coronary total arterial occlusions in man: systematic review of assessment and pathophysiology

BACKGROUND

Anatomical and functional assessment of the collateral circulation of the heart in total arterial occlusions is challenging, and this is particularly true of the microcirculation. The pathophysiology of the collateral circulation has historically been and remains of considerable research focus but with diverging and sometimes conflicting results. Our purpose was to conduct a systematic review on the assessment and pathophysiology of the collateral circulation of the heart in total coronary arterial occlusions.

METHODS

We extracted data from Pubmed, Ovid, EMBASE, and Cochrane database from 1966 to December 2012. Two investigators independently reviewed the identified articles for eligibility and extracted the data.

RESULTS

Seventy-seven studies met inclusion criterion. An invasive assessment of the collateral circulation with pressure and/or Doppler wires is the gold standard in the assessment of collateral physiology and anatomy, although this can only be undertaken after successful passage of the sensor in the true lumen of the occluded vessel. A collateral circulation can provide resting metabolic requirements for the heart but invariably cannot meet demands on stress irrespective of the degree of collateralization as assessed by coronary angiography. In the case of myocardium subtending a totally occluded epicardial artery coronary collateral grading systems or physiological assessment of collateral flow is only moderately sensitive and poorly specific at predicting viability. Regression of collaterals seems more profound in totally occluded arteries versus nonoccluded lesions postrevascularization.

CONCLUSIONS

Key controversies in the assessment and pathophysiology of the collateral circulation of the heart in total coronary arterial occlusions are systematically evaluated.

Utility of fractional flow reserve to determine treatment after recent large myocardial infarction with severe left ventricular dysfunction

Evaluation of ischemia and the extent of viable myocardium is required prior to consideration of revascularizing a lesion after a myocardial infarction in which there is hypo- or akinesis. We present a case in which we utilized fractional flow reserve (FFR) of a lesion in a patient whose nuclear study 7 days after infarction suggested minimal viability in the infarct zone. After FFR was positive, stenting was performed with recovery of a large amount of viable myocardium at 1 month as shown on nuclear study. This case illustrates that if ischemia is demonstrated by FFR in an infarct-related artery even with minimal viability by nuclear study, revascularization may result in significant myocardial recovery.

Fractional flow reserve and myocardial viability as assessed by SPECT perfusion scintigraphy in patients with prior myocardial infarction

BACKGROUND

In patients with previous myocardial infarction (MI), assessment of myocardial viability and physiological significance of coronary artery stenoses are essential for appropriate guidance of revascularization. The aim of the study was to evaluate the relation between fractional flow reserve (FFR) and myocardial viability as assessed by gated SPECT MIBI perfusion scintigraphy in patients with previous MI undergoing elective PCI.

METHODS

The study population consisted of 26 patients (mean age 55 ± 7 years; 21 male) with a previous MI and a significant coronary stenosis in a single infarct-related coronary vessel for which PCI was being performed. In all patients, FFR was evaluated before and immediately after PCI. SPECT imaging was done before and 3 ± 1 months after PCI. A region representing the MI was considered viable if MIBI uptake was ≥55% of the normal region. Improvement in perfusion after revascularization was considered achieved if perfusion abnormalities decreased by 5% or more and there was a decrease in segmental score of ≥1 in three segments in PCI-related vascular territory.

RESULTS

Extent of perfusion abnormalities decreased from 32 ± 16% to 27 ± 19% after PCI (P < .001). In patients with myocardial viability in comparison to patients with no viability, there was significant difference in FFR before PCI (.57 ± .14 vs .76 ± .12, P = .002), despite almost the same values of diameter stenosis of infarct-related artery (63 ± 8% vs 64 ± 3%, respectively, P = .572). In addition, FFR prior to PCI was related to improvement in perfusion abnormalities after revascularization (P = .047), as well as with peak activity of creatine-kinase measured during previous MI (r = .56, P = .005).

CONCLUSION

Lower values of FFR before angioplasty are associated with myocardial viability and functional improvement as assessed by SPECT perfusion scintigraphy.