Pressure-wire based assessment of microvascular resistance using calibrated upstream balloon obstruction: a predictor of myocardial viability

Prognostic value of microvascular resistance and its association to fractional flow reserve: a DEFINE-FLOW substudy

Objective

This study aimed to evaluate the prognostic value of hyperemic microvascular resistance (HMR) and its relationship with hyperemic stenosis resistance (HSR) index and fractional flow reserve (FFR) in stable coronary artery disease.

Methods

This is a substudy of the DEFINE-FLOW cohort (NCT02328820), which evaluated the prognosis of lesions (n=456) after combined FFR and coronary flow reserve (CFR) assessment in a prospective, non-blinded, non-randomised, multicentre study in 12 centres in Europe and Japan. Participants (n=430) were evaluated by wire-based measurement of coronary pressure, flow and vascular resistance (ComboWire XT, Phillips Volcano, San Diego, California, USA).

Results

Mean FFR and CFR were 0.82±0.10 and 2.2±0.6, respectively. When divided according to FFR and CFR thresholds (above and below 0.80 and 2.0, respectively), HMR was highest in lesions with FFR>0.80 and CFR<2.0 (n=99) compared with lesions with FFR≤0.80 and CFR≥2.0 (n=68) (2.92±1.2 vs 1.91±0.64 mm Hg/cm/s, p<0.001). The FFR value was proportional to the ratio between HMR and the HMR+HSR (total resistance), 95% limits of agreement (−0.032; 0.019), bias (−0.003±0.02) and correlation (r²=0.98, p<0.0001). Cox regression model using HMR as continuous parameter for target vessel failure showed an HR of 1.51, 95% CI (0.9 to 2.4), p=0.10.

Conclusions

Increased HMR was not associated with a higher rate of adverse clinical events, in this population of mainly stable patients. FFR can be equally well expressed as HMR/HMR+HSR, thereby providing an alternative conceptual formulation linking epicardial severity with microvascular resistance.

Trial registration number

NCT02328820.

Novel application of quantitative flow ratio for predicting microvascular dysfunction after ST-segment-elevation myocardial infarction

OBJECTIVES

This study evaluated quantitative flow ratio (QFR) to predict microvascular dysfunction (MVD) in patients with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

QFR is a novel approach for the rapid computation of fractional flow reserve based on three-dimensional quantitative coronary angiography. We hypothesized that QFR computation could be used to predict MVD after STEMI.

METHODS

Indexes such as contrast-flow QFR (cQFR), fixed-flow QFR (fQFR), and hyperemic flow velocity (HFV) were calculated in 130 STEMI patients with culprit lesion with ≥50% diameter stenosis and TIMI flow grade 2/3 in the spontaneously recanalized culprit artery on initial angiography. MVD was defined as microvascular obstruction determined by contrast-enhanced cardiac magnetic resonance at a median of 5 days after percutaneous coronary intervention.

RESULTS

Patients were divided into the MVD group (76/130, 58.5%) and non-MVD group (54/130, 41.5%). Patients with MVD had higher cQFR-fQFR value (0.080 ± 0.058 vs. 0.038 ± 0.039, p < .001) and lower modeled HFV (0.096 ± 0.044 vs. 0.144 ± 0.041 m/s, p < .001). Receiver operator characteristic curve analysis revealed that both the cQFR-fQFR value (area under the curve, AUC = 0.716, p < .001) and modeled HFV (AUC = 0.805, p < .001) had high specificity and positive predictive value to predict MVD. In multivariable logistic analysis, cQFR-fQFR was identified as an independent predictor of MVD (odds ratio = 9.800, p < .001).

CONCLUSIONS

This proof-of-concept study suggested that QFR computation may be a useful tool to predict MVD after STEMI (Trial Registration:NCT03780335).

Resting Pd/Pa and haemodynamic relevance of coronary stenosis as evaluated by fractional flow reserve

BACKGROUND

Fractional flow reserve (FFR) currently represents the gold standard in the evaluation of the haemodynamic relevance of coronary stenoses. However, both intracoronary and intravenous adenosine may be tolerated poorly by some patients. Therefore, considerable interest had been focused in the last few years on new adenosine-free indexes to define the haemodynamic relevance of coronary stenoses. So far, few data have been reported on resting Pd/Pa and its correlation with FFR as evaluated with high-dose intracoronary adenosine administration, which is the aim of the current study.

MATERIALS AND METHODS

FFR was assessed in 120 patients with 137 intermediate lesions during cardiac catheterization by a pressure-recording guidewire (PrimeWire). FFR was calculated as the ratio of the distal coronary pressure to the aortic pressure at hyperaemia. Intracoronary doses of adenosine were administered up to 720 μg as intracoronary boli. Exclusion criteria were as follows: (a) allergy to adenosine; (b) baseline bradycardia (heart rate <50 bpm); (c) hypotension (blood pressure <90 mmHg); and (d) refusal to provide signed informed consent.

RESULTS

High doses of intracoronary adenosine were well tolerated, with no major side effects. Increasing doses up to 720 μg progressively decreased FFR values and increased the percentage of patients showing an FFR less than 0.80. Resting Pd/Pa showed good accuracy in the identification of patients with significant FFR values (<0.80) [area under the curve=0.9 (0.84-0.96), P<0.0001]. Using receiver-operating characteristic curves, we identified a threshold less than 0.93 as the best accurate cut-off value in the prediction of a positive FFR value. A value up to 0.88 was associated with a 100% positive predictive value, whereas a value of at least 0.95 was associated with a 95% negative predictive value.

CONCLUSION

This study showed that in intermediate lesions, resting Pd/Pa was related linearly to FFR. We identified 0.93 as the best cut-off value in the prediction of haemodynamically significant coronary stenosis as evaluated by FFR. However, cut-off values of 0.88 and 0.95 could provide the maximal predictive positive and negative values, suggesting the additional use of FFR only in patients with resting values within this range.

The Relationship between Microcirculatory Resistance and Fractional Flow Reserve in Patients with Acute Myocardial Infarction

BACKGROUND AND OBJECTIVES

It was demonstrated that the fractional flow reserve (FFR) with partial balloon obstruction may have implications for assessing viable myocardium. In a different way, the index of microcirculatory resistance (IMR) was introduced as a useful indicator for assessing microvascular function. We evaluated the relationship between the FFR0.8 and the IMR.

SUBJECTS AND METHODS

We studied 48 consecutive patients who had undergone coronary intervention for acute myocardial infarction (AMI). After revascularization using stent(s), an undersized short balloon was positioned inside the stent and inflated to create a specific normalized pressure drop of FFR (distal coronary/aortic pressure=0.80) at rest. The FFR0.8 was obtained during hyperemia with the fixed state balloon-induced partial obstruction. IMR was measured by three injections of saline. The association between the FFR0.8 and the IMR was investigated.

RESULTS

The mean age of the patients was 60±12 years and 36 (75%) overall presented with ST-segment elevation myocardial infarction. The mean FFR0.8 was 0.68±0.06. A statistically significant correlation between the FFR0.8 and the log-transformed IMRtrue (LnIMRtrue) was found through a multivariable linear regression analysis (β=0.056, p<0.001). Both the FFR0.8 and the LnIMRtrue had a positive correlation with the log-transformed peak troponin I (TnI) with statistical significance (r(2)=0.119, p=0.017; r(2)=0.225, p=0.006, respectively).

CONCLUSION

There was a positive correlation between the LnIMRtrue and the FFR0.8. Both of the values were associated with peak TnI. Those values may be used as appropriate surrogate measures of microvascular function after AMI.

Prediction of Fractional Flow Reserve without Hyperemic Induction Based on Resting Baseline Pd/Pa

BACKGROUND AND OBJECTIVES

The purposes of this study are 1) to investigate the relationship between resting baseline Pd/Pa, determined by the ratio of the pressures proximal (Pa) and distal (Pd) to the target lesion before, inducing hyperemia and fractional flow reserve (FFR) and 2) to identify a resting baseline Pd/Pa range that might reliably preclude the need for hyperemic induction.

SUBJECTS AND METHODS

A total of 622 pressure wire data sets obtained from intermediate stenotic lesions were analyzed.

RESULTS

There was a good linear relationship between resting baseline Pd/Pa and FFR (r=0.746, p<0.001). Receiver-operating characteristic curves of the resting baseline Pd/Pa with FFR ≤0.80 as the reference variable showed an area under the curve of 0.89 (95% confidence intervals 0.863-0.914, p<0.001) with a diagnostic accuracy of 82.3% when the resting baseline Pd/Pa was ≤0.92. These results showed that certain cutoff values can reliably predict FFR, whether positive or negative. The resting baseline Pd/Pa >0.95 (n=257, 41.3%) had a negative predictive value (NPV) of 98.1% and a sensitivity of 97.3%. the resting baseline Pd/Pa ≤0.88 (n=65, 10.5%) had a positive predictive value (PPV) of 96.2% and a specificity of 99.8%. These were consistent regardless of coronary vessel, lesion location, lesion length, or degree of stenosis.

CONCLUSION

In intermediate lesions, the resting baseline Pd/Pa was linearly related to FFR. A certain range of the resting baseline Pd/Pa values had an excellent NPV with high sensitivity or excellent PPV with high specificity for determining the lesion significance.