Discordance between pressure drift after wire pullback and intracoronary distal pressure offset affects stenosis physiology appraisal

Effect of prolonged pressure equalization on final drifting during pressure wire studies

Pressure drifting is a troublesome error in invasive coronary function tests. This study aimed to evaluate the relationship between prolonged and short-time pressure equalizations in pressure drifting. Pressure drifting was defined as the pressure gradient between the mean pressure of the distal wire sensor (Pd) and aortic pressure (Pa) when the wire was withdrawn to the tip of the guiding catheter. Significant drifts 1 and 2 were defined as the absolute values of pressure gradients > 2 and > 3 mmHg, respectively. A logistic regression model was used to evaluate the associations between prolonged pressure equalization and each pressure drifting. The prolonged pressure equalization strategy was associated with a lower incidence of drift 1 than the short-time pressure equalization strategy (6.84% vs. 16.92%, p < 0.05). However, no statistical differences were found in the incidence of drift 2 between the prolonged and short-time pressure equalization strategies (4.27% vs. 7.69%, p = 0.34). In the multivariable regression model, only the prolonged pressure equalization strategy predicted a lower incidence of pressure drift 1. In conclusion, the prolonged pressure equalization strategy was associated with a lower incidence of significant pressure drifting with more stringent thresholds than the short-time pressure equalization strategy.

Aortic Stenosis: Haemodynamic Benchmark and Metric Reliability Study

Aortic stenosis is a condition which is fatal if left untreated. Novel quantitative imaging techniques which better characterise transvalvular pressure drops are being developed but require refinement and validation. A customisable and cost-effective workbench valve phantom circuit capable of replicating valve mechanics and pathology was created. The reproducibility and relationship of differing haemodynamic metrics were assessed from ground truth pressure data alongside imaging compatibility. The phantom met the requirements to capture ground truth pressure data alongside ultrasound and magnetic resonance image compatibility. The reproducibility was successfully tested. The robustness of three different pressure drop metrics was assessed: whilst the peak and net pressure drops provide a robust assessment of the stenotic burden in our phantom, the peak-to-peak pressure drop is a metric that is confounded by non-valvular factors such as wave reflection. The peak-to-peak pressure drop is a metric that should be reconsidered in clinical practice. The left panel shows manufacture of low cost, functional valves. The central section demonstrates circuit layout, representative MRI and US images alongside gross valve morphologies. The right panel shows the different pressure drop metrics that were assessed for reproducibility.

Reference values for intracoronary Doppler flow velocity-derived hyperaemic microvascular resistance index

BACKGROUND

Invasive assessments of microvascular function are rapidly becoming an integral part of physiological assessment in chronic coronary syndromes.

OBJECTIVE

We aimed to establish a reference range for Doppler flow velocity-derived hyperaemic microvascular resistance index (HMR) in a cohort of angina with no significant epicardial coronary obstruction (ANOCA) patients with no structural pathophysiological alterations in the coronary circulation.

METHODS

The reference population consisted of ANOCA patients undergoing invasive coronary vasomotor function assessment who had a coronary flow reserve (CFR) >2.5, and had either (1) tested negatively for spasm provocation (n = 12) or (2) tested positively with only angina at rest (n = 29). A reference range for HMR was established using a non-parametric method and correlations with clinical characteristics were determined using a spearman rank correlation analysis.

RESULTS

In 41 patients median HMR amounted to 1.6 mmHg/cm/s [Q1, Q3: 1.3, 2.2 mmHg/cm/s]. The reference range for HMR that is applicable to 95% of the population was 0.8 mmHg/cm/s (90% CI: 0.8-1.0 mmHg/cm/s) to 2.7 mmHg/cm/s (90% CI: 2.6-2.7 mmHg/cm/s). No significant correlations were found between HMR and clinical characteristics.

CONCLUSION

In this reference population undergoing invasive coronary vasomotor function testing, the 90% confidence interval of the HMR upper limit of normal ranges from 2.6 to 2.7 mmHg/cm/s. A > 2.5 mmHg/cm/s HMR threshold can be used to identify abnormal microvascular resistance in daily clinical practice.