Why the study?
Guidelines recommend coronary slow flow phenomenon diagnosed by CTFC to identify coronary microvascular dysfunction, but the utility of CTFC to diagnose CMD and CED needed validation.
Does coronary slow flow phenomenon accurately diagnose coronary microvascular dysfunction or coronary endothelial dysfunction in patients with angina and nonobstructed coronary arteries?
Does coronary slow flow phenomenon accurately diagnose coronary microvascular dysfunction or coronary endothelial dysfunction in patients with angina and nonobstructed coronary arteries?
Coronary slow flow phenomenon and corrected TIMI frame count are not reliable diagnostic markers for coronary microvascular or endothelial dysfunction, challenging current guideline recommendations.
Background Guidelines recommend that coronary slow flow phenomenon (CSFP), defined as corrected thrombolysis in myocardial infarction frame count (CTFC) > $$ > $$ 27, can diagnose coronary microvascular dysfunction (CMD) in patients with angina and nonobstructed coronary arteries. CSFP has also historically been regarded as a sign of coronary endothelial dysfunction (CED). We sought to validate the utility of CTFC, as a binary classifier of CSFP and as a continuous variable, to diagnose CMD and CED. Methods and Results Patients with angina and nonobstructed coronary arteries had simultaneous coronary pressure and flow velocity measured using a dual sensor‐tipped guidewire during rest, adenosine‐mediated hyperemia, and intracoronary acetylcholine infusion. CMD was defined as the inability to augment coronary blood flow in response to adenosine (coronary flow reserve <2.5) and CED in response to acetylcholine (acetylcholine flow reserve ≤1.5); 152 patients underwent assessment using adenosine, of whom 82 underwent further acetylcholine testing. Forty‐six patients (30%) had CSFP, associated with lower flow velocity and higher microvascular resistance as compared with controls (16.5 ± ± 6.9 versus 20.2 ± ± 6.9 cm/s; P =0.001 and 6.26 ± ± 1.83 versus 5.36 ± ± 1.83 mm Hg/cm/s; P =0.009, respectively). However, as a diagnostic test, CSFP had poor sensitivity and specificity for both CMD (26.7% and 65.2%) and CED (21.1% and 56.0%). Furthermore, on receiver operating characteristics analyses, CTFC could not predict CMD or CED (area under the curve, 0.41 [95% CI, 0.32%–0.50%] and 0.36 [95% CI, 0.23%–0.49%], respectively). Conclusions In patients with angina and nonobstructed coronary arteries, CSFP and CTFC are not diagnostic of CMD or CED. Guidelines supporting the use of CTFC in the diagnosis of CMD should be revisited.
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Dutta et al. (2022) studied this question.
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