Mismatch Between Results of Myocardial Fractional Flow Reserve (FFR) Measurements and Myocardial Perfusion SPECT for Identification of the Severity of Ischemia: Pitfall of FFR in Patients With Prior Myocardial Infarction

Abstract

SUMMARYWe experienced two rare cases of mismatch between the results of FFR and myocardial perfusion SPECT for identification of myocardial ischemia after myocardial infarction. If a FFR cutoff value of 0.75 is applied as in angina patients to patients with myocardial infarction, the severity of ishemia may be underestimated. (Jpn Heart J 2004; 45: 867-872) Key words: FFR (fractional flow reserve), Myocardial perfusion SPECT, Myocardial infarction MYOCARDIAL fractional flow reserve (FFR) is an indicator of the level of coronary vascular function, and differs from the coronary flow reserve. Although the latter is defined as the ratio of coronary blood flow at maximum load to coronary blood flow at rest, FFR is calculated as the ratio of the distal coronary pressure to the aortic pressure during maximal hyperemia, and serves as an indicator of the functional severity of coronary artery stenosis.

Integrated Myocardial Perfusion Imaging Diagnostics Improve Detection of Functionally Significant Coronary Artery Stenosis by 13 N-ammonia Positron Emission Tomography

“…2,13 In managing patients with suspected coronary artery disease, optimal thresholds of quantitative 11 or invasive coronary angiography 6,8,11 ), FFR, combination of both tests, 9,12,23 or relative PD combined with ST-segment depression and clinical history of angina. 10 It is well known that angiographic determinations of stenosis and related myocardial ischemia often diverge, 15,18,[33][34][35][36][37][38] so interpretation of previous study results must consider the methods used to define lesion-specific ischemia. Such discrepancies may even present in lesions beyond intermediate-range severity.…”

Fractional flow reserve in acute coronary syndromes: A review

“…It is recognised that FFR values in the culprit vessel are higher during acute episodes when compared to measurements made after the microcirculation has had some time to recover [9], [10]. It is postulated that this is due to a reduction in the level of attainable hyperaemia in the culprit vessel due to embolisation of thrombus and plaque, ischaemic microvascular dysfunction and myocardial stunning [11].…”

“…Tani et al described an exploratory finding in patients post AMI who had related wall ischaemia on myocardial perfusion single-photon emission computed tomography (SPECT), but had non-physiologically significant FFR measurements of 0.87 and 0.89 in the left anterior descending and right coronary arteries respectively. The mismatch between the diagnostic modalities led the authors to suggest applying caution when interpreting FFR in culprit lesions post MI [10]. It is important to note, however, that both of these small studies measured FFR in the peri-infarct period in culprit arteries only and no assessments were performed in non-culprit bystander lesions.…”

“…The major advantages associated with FFR measurements include reproducibility, high degree of spatial resolution [13], high specificity when compared with non-invasive modalities such as myocardial SPECT [10]. FFR provides a practical assessment of physiological significance which can be used to provide immediate answers in the cardiac catheterisation laboratory.…”

“…It is not uncommon for patients with AMI to present with concurrent atrio-ventricular block, bradycardia, hypotension, severe airway diseases or cardiogenic shock precluding the use of adenosine to induce hyperaemia in this group [10]. These factors mean that a proportion of patients presenting with AMI would be ineligible for FFR assessment, and other functional or anatomical assessments would be required.…”