Angiographic underestimation of disease severity in the left anterior descending artery: a fractional flow reserve analysis

Impact of height difference between coronary ostium and location of intracoronary pressure sensor on fractional flow reserve measurements

BACKGROUND

During fractional flow reserve (FFR) measurements, distal coronary pressure (Pd) can be influenced by hydrostatic pressure changes resulting from the height difference (HD) between the coronary ostium and the location of the distal pressure sensor.

AIMS

We investigated the effect of aortocoronary HD on the FFR measurements in each coronary artery.

METHODS

In this retrospective cohort study, we analyzed 257 patients who underwent FFR measurements and coronary computed tomography (CCTA) within a year. Using CCTA, we measured HD as the vertical distance between the coronary ostium and a matched point of the distal coronary pressure sensor identified on coronary angiography.

RESULTS

The location of the Pd sensor was higher than the coronary ostium in the left anterior descending artery (LAD) (-4.64 ± 1.15 cm) and lower than the coronary ostium in the left circumflex artery (LCX) (2.54 ± 1.05 cm) and right coronary artery (RCA) (2.03 ± 1.28 cm). The corrected FFR values by HD were higher in the LAD (0.78 ± 0.09 to 0.82 ± 0.09, P<0.01) and lower in the LCX and RCA than the original FFR values (0.87 ± 0.07 to 0.85 ± 0.08, P<0.01; 0.87 ± 0.10 to 0.86 ± 0.10, P<0.01, respectively). Using an FFR cut-off value of 0.8, the concordance rates between the FFR and corrected FFR values were 77.8%, 95.2%, and 100% in the LAD, LCX, and RCA, respectively.

CONCLUSION

HD between the coronary ostium and the distal coronary pressure sensor may affect FFR measurements and FFR-guided treatment decisions for coronary artery disease.

Incessant Refractory Polymorphic Ventricular Tachycardia After Coronary Artery Bypass Graft

Polymorphic ventricular tachycardia (PVT) post coronary artery bypass (CABG) surgery is associated with acute myocardial ischemia, hemodynamic instability, and metabolic derangements. When acute ischemia is suspected, a comprehensive investigation for reversible causes is justified to improve patient outcomes. We present a curious case of incessant, refractory PVT in a patient with an unknown etiology requiring percutaneous coronary intervention (PCI) post CABG. The patient was a 73-year-old female with multiple comorbidities who presented to the hospital with anginal chest pain for one day. Initial electrocardiogram (EKG) showed sinus tachycardia with ST-segment depressions in the inferior-lateral leads. Initial cardiac troponin I was elevated at 28.280 ng/mL. Dual antiplatelet therapy and heparin were started. Urgent coronary angiography revealed significant triple-vessel disease, and she subsequently underwent three-vessel CABG. Her postoperative course was complicated by PVT refractory to all antiarrhythmic therapy and ventricular fibrillatory (VF) arrest with the recovery of spontaneous circulation after defibrillation and amiodarone bolus. Despite normal electrolytes and discontinuation of all QT-prolonging agents, PVT persisted. Urgent coronary angiography revealed a patent venous graft to a previously underappreciated severely stenotic distal segment of the left anterior descending artery (LAD). She underwent PCI of the culprit lesion with the termination of PVT. Although acute graft failure is regularly the culprit for acute myocardial infarction perioperatively, emergent coronary angiography post coronary bypass surgery revealed patent grafts and a previously underestimated severe coronary lesion contributing to ongoing ischemia. Post CABG percutaneous coronary intervention (PCI) yielded a complete resolution of her arrhythmia.

Does fractional flow reserve overestimate severity of LAD lesions?

BACKGROUND

Fractional Flow Reserve (FFR) is increasingly used to estimate the severity of coronary stenoses, prior to coronary revascularization. However, it has been suggested that FFR overestimates the severity of Left Anterior Descending (LAD) lesions. Our aim was to verify whether in patients without ischemia on Myocardial Perfusion Imaging, FFR of the LAD is more often abnormal in comparison to FFR of other coronary arteries.

METHODS

Prospective cohort study of consecutive patients who underwent FFR measurement because of persistent or worsening of angina complaints, within 6 months after normal Myocardial Perfusion Imaging. FFR measurements of a graft or diagonal branch were excluded. A FFR ≤ 0.80 denoted a functionally relevant stenosis.

RESULTS

In 133 patients, 167 FFR measurements were performed, of which 85 in the LAD. Mean age of the patients was 64.8 ± 10.5 years, 40% were women. There were no differences in baseline characteristics between patients undergoing LAD and non-LAD measurements. An abnormal FFR was observed in 35.3% of the LAD measurements, compared to 9.8% in the non-LAD measurements (P = 0.001). Also after adjusting for age and gender, the FFR remained more frequently abnormal in the LAD with OR 5.2 (95% CI 2.2 to 12.3). Of the abnormal FFR LAD measurements, 70% were visually considered non-obstructive on invasive angiography.

CONCLUSIONS

In selected patients without ischemia on MPI, FFR measurement of the LAD is significantly more often abnormal. The majority of these patients has no obstructive lesions on invasive angiography. Possibly, FFR overestimates severity of LAD lesions, with risk of unnecessary revascularization.