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Pressure-temperature sensor-tipped wire coronary flow capacity may predict prognosis after PCI
Measurement of coronary flow capacity using a pressure-temperature sensor-tipped wire is feasible and may help identify patients with CAD who would benefit most from PCI, according to new data.
The clinical value of coronary flow capacity has been confirmed in previous studies using Doppler-flow wire and PET. However, the utility of these techniques is limited in daily clinical practice. In contrast, the pressure-temperature sensor-tipped wire is routinely used to measure fractional flow reserve and can examine coronary flow reserve by thermodilution method, and FFR and thermodilution-derived coronary flow reserve could be obtained in nearly all patients with CAD, according to Rikuta Hamaya, MD, from the cardiovascular division at Tsuchiura Kyodo General Hospital in Japan, and colleagues.
“Thus, we tried to explore and examine the feasibility of coronary flow capacity mapping by pressure-temperature sensor-tipped wire-derived physiological indices,” Hamaya told Cardiology Today’s Intervention.
Risk stratification
From 2011 to 2017, Hamaya and colleagues assessed 643 native de novo lesions using a pressure-temperature sensor-tipped wire (PressureWire, Abbott/St. Jude Medical) in patients with stable CAD seen at their institution in Japan.
Using thresholds of coronary flow reserve and the corresponding inverse of thermodilution-derived mean transit time under hyperemia, patients were categorized as having normal (63.4%), mildly reduced (15.1%), moderately reduced (9.8%) and severely reduced (11.7%) pressure-temperature sensor-tipped wire-derived coronary flow capacity. Revascularization was indicated based on symptoms, noninvasive test results and FFR values.
Angiographic stenosis and physiological properties of the lesions were significantly stratified according to pressure-temperature sensor-tipped wire-derived coronary flow capacity, as were the frequency of abnormal values of FFR of 0.8 or less and coronary flow reserve less than 2, and the ratio of angiographic nonsignificant CAD, defined as diameter stenosis less than 50% (P < .001 for all.
Revascularization was performed in 47.8% of patients with normal coronary flow capacity, 47.4% of those with mildly reduced coronary flow capacity, 73% of those with moderately reduced coronary flow capacity and 82.7% of those with severely reduced coronary flow capacity. About 17% of patients with severely reduced coronary flow capacity for whom PCI was deferred had high microvascular dysfunction as defined by index of microvascular resistance values (median, 42.9).
Coronary flow capacity and MACE
During a median follow-up of 2.4 years, the overall rate of MACE — a composite of CV death, nonfatal MI and hospitalization due to congestive HF — was 10.4%. Results linked advanced impairment of coronary flow capacity to significantly increased incidence of MACE, except among patients with severely reduced coronary flow capacity (P = .002). This group, of whom 82.7% underwent PCI, had similar clinical outcomes compared with the other groups (P = .86).
In univariate Cox proportional analysis, diameter stenosis less than 50%, FFR, coronary flow reserve and coronary flow capacity were associated with MACE incidence. In multivariate analysis, independent predictors of MACE included moderately reduced coronary flow capacity (HR = 2.273; 95% CI, 1.051-4.941), FFR (HR = 0.075; 95% CI, 0.006-0.875) and dyslipidemia (HR = 1.751; 95% CI, 1.034-3.086).
“The moderately reduced coronary flow capacity group, not the severely reduced coronary flow capacity group, had the worst clinical outcome in the total cohort,” Hamaya said. “This result led us to explore the possible benefit of PCI in the severely reduced coronary flow capacity group in a subgroup analysis.”
Hamaya and colleagues found that coronary flow capacity improved to normal levels after PCI in 60.4% of the 230 patients[RH1] who had severely reduced coronary flow capacity before the procedure. MACE incidence was also significantly lower in this subgroup compared with those showing no improvement.
The relatively favorable outcomes noted in the group with severely reduced coronary flow capacity before PCI may be partially attributable to the high prevalence of normal coronary flow capacity after PCI, the researchers wrote.
‘Beyond a stenosis-centered approach’
Overall, the results from the study are encouraging, according to Hamaya.
“Coronary flow capacity categorization is a promising approach toward understanding whole flow characteristics in CAD and is feasible using a single PressureWire in almost all examined patients in the cath lab,” he told Cardiology Today’s Intervention. “The combination of coronary flow capacity categorization and FFR might specify the subset of patients who could achieve potentially improved clinical outcomes with PCI and risk-stratify the patients with coronary flow impairment on top of FFR.”
However, whether this approach to revascularization decision-making leads to better outcomes, compared with an FFR-guided approach, requires validation in further studies, Hamaya said. In the future, the researchers would also like to validate the pressure-temperature sensor-tipped wire-derived coronary flow capacity categorization for epicardial and microvascular disease using PET or cardiac magnetic resonance imaging studies.
In an accompanying editorial, Tim P. van de Hoef, MD, PhD, and Jan J. Piek, MD, PhD, both from the AMC Heartcenter at the Academic Medical Center in Amsterdam, highlighted the study’s limitations, such as the potential for selection bias and the fact that coronary flow capacity obtained through thermodilution may be affected by the use of the thermodilution technique.
Nevertheless, the study reaffirms the diagnostic value of coronary flow measurements in addition to coronary pressure when treating ischemic heart disease, they noted.
“The time has come to move beyond a stenosis-centered approach towards an integrated analysis of the epicardial vasculature and microvascular bed in patients with ischemic heart disease. The waves are there, the wind is calling, we just have to adjust our sails,” van de Hoef and Piek wrote. – by Melissa Foster
Disclosure: The authors report no relevant financial disclosures. Piek and van de Hoef report they have served as speakers at educational events sponsored by Abbott/St. Jude Medical, Boston Scientific and Volcano/Philips.