Physician Education

Invasive Diagnostic and Treatment Pathway for Patients With ANOCA:

Tips and Tricks

Hady Lichaa and James Torey, January 2023 

Patient Preparation: 

Microvascular assessment can occur as either a scheduled or an elective procedure, occurring after initial angiographic findings revealing the absence of obstructive epicardial coronary artery disease. In both scenarios, patient preparation is necessary for obtaining precise and reliable microvascular measurements. 

Most notably, maximal hyperemia associated with intravenous (IV) adenosine administration is likely to be blunted in patients with recent (< 24 hours) ingestion of caffeine (1). This is an important detail because a large proportion of patients who are scheduled for microvascular testing may have ingested caffeinated beverages within 24 hours prior to the procedure, since they are only instructed to avoid eating or drinking after midnight on the day of the procedure.

Another important aspect is medication management prior to the scheduled procedure. If the goal of the study is to establish the diagnosis (as opposed to monitoring treatment response), it is recommended to hold cardiac medications that may affect the results for 24-48 hours (depending on their respective half-lives). This includes beta blockers, renin-angiotensin receptor antagonists, calcium channel blockers, and nitrates, which may have to be transiently switched to alternative anti-hypertensive medications that do not have direct cardiac activity, such as clonidine, hydralazine, or doxazosin. 

Other factors need to be taken into account in the interpretation of the hemodynamic results. For instance, obesity and lower microcirculatory resistance states are linked to a hypotensive response to IV adenosine. This loss in perfusion pressure leads to protective microcirculatory vasoconstriction and subsequent rise in distal resistance that may attenuate trans-stenotic gradients during an otherwise stable hyperemia. (2,3) The opposite effect occurs in hypertensive patients, which can lead to underestimation of the degree of microvascular dysfunction. (4) Left ventricular hypertrophy has also been associated with a poor response to hyperemic agents with resultant overestimation of the obtained results. (5) 

Building a microvascular program: 

A key factor in establishing a microvascular program is “buy in” from the supporting staff. Education is important on multiple levels in order for a program to succeed. Most importantly, the Cath Lab staff should be thoroughly educated on the benefits of microvascular testing with regards to improved clinical outcomes, as seen in the CorMicA trial (6), and the fact that microvascular/vasospastic testing is now an integral part of the chest pain guidelines (7).

We also believe that an effective program requires an interventional cardiologist as a champion who not only educates other physicians and staff but who also takes ownership of the success of the program as well as having a passion for diagnosing/treating a patient population who is often frustrated from frequent non-diagnostic healthcare visits. The implications of the more favorable clinical outcomes for patients with chest pain and the healthcare system need to be clearly articulated early in the building process (6).

On the administrative side, it is essential to outline the other favorable aspects of the program, including patient satisfaction, cost-effectiveness and avoidance of unnecessary testing and frequent hospitalizations/emergency department evaluations. We have experienced that integration of microvascular testing in the cath lab not only offers the advantage of thorough physiologic assessment, but also reduces procedural time and accelerates patient throughput.

References

1. Submaximal adenosine-induced coronary hyperaemia with 12 h caffeine abstinence: implications for clinical adenosine perfusion imaging tests. Carlsson M1, Jögi J, Bloch KM, Hedén B, Ekelund U, Ståhlberg F, Arheden H. Clin Physiol Funct Imaging. 2014 Jan 12. doi: 10.1111/cpf.12125.

2. Improvement in coronary haemodynamics after percutaneous coronary intervention:  assessment using instantaneous wave-free ratio.  Nijjer SS, et al. Heart 2013;0:1–9.

3. Association between coronary lesion severity and distal microvascular resistance in patients with coronary artery disease. Chamuleau SAJ, Siebes M, Meuwissen M, et al. Am J Physiol Heart Circ Physiol 2003;285:H2194–200.

4. Low coronary microcirculatory resistance associated with profound hypotension during intravenous adenosine infusion: implications for the functional assessment of coronary stenoses. Echavarría-Pinto M1, Gonzalo N, Ibañez B et al. Circ Cardiovasc Interv. 2014 Feb;7(1):35-42

5. Coronary pressure measurement and fractional flow reserve. Pijls NHJ, De Bruyne B. Heart 1998;80:539–542.

6. Ford TJ, Stanley B, Sidik N, Good R, Rocchiccioli P, McEntegart M, Watkins S, Eteiba H, Shaukat A, Lindsay M, Robertson K, Hood S, McGeoch R, McDade R, Yii E, McCartney P, Corcoran D, Collison D, Rush C, Sattar N, McConnachie A, Touyz RM, Oldroyd KG, Berry C. 1-Year Outcomes of Angina Management Guided by Invasive Coronary Function Testing (CorMicA). JACC Cardiovasc Interv. 2020 Jan 13;13(1):33-45. doi: 10.1016/j.jcin.2019.11.001. Epub 2019 Nov 11. PMID: 31709984; PMCID: PMC8310942.

7. Gulati M, Levy PD, Mukherjee D, Amsterdam E, Bhatt DL, Birtcher KK, Blankstein R, Boyd J, Bullock-Palmer RP, Conejo T, Diercks DB, Gentile F, Greenwood JP, Hess EP, Hollenberg SM, Jaber WA, Jneid H, Joglar JA, Morrow DA, O'Connor RE, Ross MA, Shaw LJ. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2021 Nov 30;144(22):e368-e454. doi: 10.1161/CIR.0000000000001029. Epub 2021 Oct 28. Erratum in: Circulation. 2021 Nov 30;144(22):e455. PMID: 34709879.