Background: A single small study (n=97) has suggested that absence of dicrotic notch (DN) in the coronary artery, distal to an intermediate stenosis, may indicate a significant stenosis, proven by an abnormal fractional flow reserve (FFR). This finding has neither been evaluated by other studies nor compared against other, more established, non hyperemic indices like Pd/Pa. It is unclear if DN is representative of coronary stenosis or coronary stiffness.
Methods: Of the 926 FFR measurements performed in a large tertiary care center over last 4 years, we included 405 measurements after excluding tracings with inadequate baseline data and absent aortic DN. Tracings with pre-adenosine measurement with 8 cardiac cycles were printed and distal dicrotic notch (DDN) was characterized visually into four types, i.e., full notch, partial notch, definite change in angle of descending limb at the end of systole, and absent DN, by two different observers. Operating test characteristics of DDN were measured against the criterion standard of FFR ≤0.8 to detect significant ischemia. Coronary calcium score (CaSc), as a marker for coronary stiffness of the vessels, was evaluated by CT.
Results: Out of 405 patients, 52 had absent DDN. The mean FFR in those with absent DDN was significantly lower (0.79 versus 0.86; p= <0.0001) compared to those with a DDN. The receiver operating area under the curve (AUC) for predicting FFR <0.80 was 0.59 (p<0.0001) for DDN, as compared to 0.89 (p= <0.0001) for baseline Pd/Pa. The sensitivity, specificity, PPV and NPV of DDN were 26%, 92%, 56%, 76%, respectively as compared to 79%, 82%, 63% and 91% for Pd/Pa < 0.93. Those with absent DDN (n=5) had a much higher CaSc (897 vs. 463; p=0.11) than those with DDN (n=32). The AUC to predict absence of DDN by CaSc was 0.62. A CaSc of 82 or lower successfully ruled out an absent DDN.
Conclusion: While DDN is associated with an abnormal FFR, our data suggest meaningfully lower performance in prediction of an abnormal FFR as compared to Pd/Pa, indicating that Pd/Pa should be preferred over DDN in clinical practice. DDN appears to be partially explained by coronary stiffness. Further studies to define the relative role of stenosis vs stiffness in regression of DDN are underway.
Hussaini S, Ullah R, Ahmad MM, Ahmad MN, Iftikhar H, Pir SH, Syed M, Muhammad M, Allaqaband S, Gupta A, Port S, Ammar K. Distal dicrotic notch in the coronary artery. Is it a function of stenosis vs. stiffness? A computed tomography and angiography correlation study. Catheter Cardiovasc Interv. 2016;87(S2):S71-2.