Author + information
- Published online August 6, 2018.
- aWeatherhead PET Center, Division of Cardiology, Department of Medicine, McGovern Medical School at UTHealth and Memorial Hermann Hospital, Houston, Texas
- bDepartment of Internal Medicine and Cardiovascular Center, Seoul National University Hospital, Seoul, Republic of Korea
- ↵∗Address for correspondence:
Dr. Nils P. Johnson, Weatherhead PET Center, McGovern Medical School at UTHealth, 6431 Fannin Street, Room MSB 4.256, Houston, Texas 77030.
“Why don't physicians follow clinical practice guidelines?” That question—the title of a broad data review and synthesis (1)—remains as valid today as it was almost 20 years ago when posed. The Cabana et al. (1) framework connected 3 major steps along a path: knowledge (understanding what do to), attitude (believing that it should be done), and behavior (actually doing it). At each step, potential barriers can thwart the desired action. Given the enormous evidence base supporting coronary physiology, its perceived underuse in clinical practice has led to a multitude of explanatory theories, including hyperemic drugs, wire properties, and reimbursement. In this issue of JACC: Cardiovascular Interventions, the ERIS study from Italy (2) provides an important opportunity to examine new and old data for each of these hypothetical barriers.
When American interventional cardiologists were asked in early 2012, “If you do not use fractional flow reserve (FFR), why not?” (3), only 1 respondent claimed it was due to a knowledge barrier (“I do not understand enough about FFR”). Additionally, <5% of responses identified attitude barriers, for example “I do not trust FFR.” Instead, the dominant responses focused on reimbursement and the time necessary to perform the procedure. A logical conclusion from this survey was that we should focus on environmental barriers to improve the penetrance of coronary physiology.
However, surveys may not accurately reflect behavior, as recently demonstrated by polling miscues in the United States election and the Brexit vote. A subsequent European study called the ISIS study (4) asked interventional cardiologists to make clinical decisions when provided with an angiogram showing an intermediate lesion in a stable patient. Importantly, the decisions were to be made “assuming ideal world conditions, without considering any financial restrictions or local regulations, but only after the best clinical practice achievable in this virtual catheterization laboratory.” In this environment, coronary physiology took just as much time (none) and cost just as much and paid just as well (nothing) as performing revascularization or administering medical therapy. Despite a complete absence of financial or logistic barriers, only 21% of lesions were evaluated using coronary physiology. A dominant 71% of decisions relied exclusively on the diagnostic angiogram, of which a slim majority (53%) matched the FFR value that had been measured but not disclosed to the operators. Although every single lesion would have been appropriate for coronary physiology under the Class I, Level of Evidence: A, recommendations in that region (5), not a single respondent selected it 100% of the time. Indeed, 27% of operators never selected coronary physiology at all.
Therefore, while operators may say that reimbursement and procedural aspects discourage coronary physiology, their actions suggest that attitude and belief in the concept of physiology-guided revascularization remain the fundamental stumbling blocks.
But does a “virtual catheterization laboratory” (4) reflect interventional cardiologists’ actions in the real world? This question was the focus of the current ERIS study from Italy (2). Their nationwide collaboration first established criteria for invasive coronary pressure evaluation based on existing guidelines (5,6) plus emerging data in acute coronary syndromes (7). Centers were selected based on a familiarity with the technique (at least 20 coronary physiology cases per year) plus a desire to participate in the project, eventually including 76 of the 258 (29%) catheterization laboratories in the country. Each center then chose a 60-day period to prospectively monitor every single coronary case, documenting if it met criteria for physiologic assessment. Whether coronary pressure measurements were performed, or reasons for not performing it, was recorded.
Of the 15,683 angiograms and 8,441 percutaneous coronary interventions (PCIs) monitored in ERIS, only 1,858 cases (7.7%) met the prespecified criteria for invasive physiologic assessment. Already these numbers raise 2 important points. First, PCI represents about one-third of the coronary volume for these Italian centers, in contrast to some countries or regions with centralized PCI hospitals where this ratio rises to a large majority. Second, that a minority of cases resulted in either PCI or coronary pressure measurement suggests an opportunity for upstream noninvasive evaluation to reduce invasive diagnostic angiography that does not result in actual or considered revascularization.
Amazingly—despite being motivated centers with experience in coronary physiology who knew that they were “being watched”—37% of lesions (681 of 1,858) did not receive coronary pressure assessment despite meeting prespecified criteria. We can only assume that this proportion would be higher (likely much higher) in routine, general practice. The second table of their manuscript (2) provides the key results, listing the operator-provided reasons for not performing physiologic assessment, organized using an established framework (1). The single dominant reason, accounting for 39% of responses, was that “clinical and angiographic data are sufficient.” A lack of feasibility (11%), time constraints (4%), adenosine cost or side effects (3%), or general costs (3%) affected a small minority of decisions.
Therefore, the ERIS study (2) confirmed the results of the ISIS study (4). Logistic and environmental barriers do not limit the uptake of coronary physiology. Rather, we think that we already know the answer and deny that physiology can improve our decisions in spite of the clinical trials that form the basis for current guidelines.
Despite these issues, attitudes can change (8) and are changing (9–14). As detailed in Table 1, several geographies have publicly reported their rates of coronary physiology uptake, in some cases at a regional or hospital level. A common but imperfect metric divides the number of pressure wires by the number of PCIs, although this easy-to-compute ratio neglects that coronary physiology can lead to medical therapy or bypass surgery (count added to the numerator but not the denominator) or that PCI of many lesions does not require physiology, for example, clear culprit lesions for an acute coronary syndrome (count added to the denominator but not the numerator). Nevertheless, temporal changes in this ratio provide a rapid and useful surrogate for behavior.
What value should the ratio of pressure wire to PCI reach? A “back of the envelope” calculation suggests that 20% is a reasonable, lower bound, assuming that 25% of PCI occurs in stable patients (15) and that 80% of these cases are eligible for pressure wire assessment (excluding chronic total occlusions and high-grade lesions in single-vessel disease with an unequivocal noninvasive study). Depending on the results of ongoing clinical trials testing coronary physiology in nonculprit lesions noted during acute presentations (FULL REVASC [Ffr-gUidance for compLete Non-cuLprit REVASCularization] trial; NCT02862119), this ratio may rise as high as 50% to 60%. The “optimal” ratio will depend on the local composition of stable versus acute patients, frequency and severity of noninvasive testing, and multivessel disease.
Encouragingly, several countries have already reached or exceeded the 20% threshold, including the United Kingdom, Sweden, Australia, and the United States. Many of these areas have reported 2- to 3-fold increases in the uptake of coronary physiology despite much more modest increases (10) or even declines (13) in PCI volume. Additionally, as noted by a review of the European PCI registry, “despite the lack of reimbursement in many countries, the use of intracoronary physiology techniques doubled from 2010 to 2015” (12).
Finally, at least 3 different countries have publicly reported intranation variations between 5- and 10-fold among centers despite a uniform healthcare system, language, and culture (9,10,14). The reasons for such wide variations deserve further attention, in addition to emerging data regarding the heterogeneity of physiologic severity uncovered among hospitals.
In summary, the ERIS study (2) helps us critically evaluate potential responses to the question “Why don't interventional cardiologists use coronary physiology?” As demonstrated by both virtual (4) and real-world (2) studies, and large temporal increases in its uptake (Table 1), factors such as cost, reimbursement, need for hyperemic drugs, or pressure sensor design and delivery play minor roles. Although operators can be reluctant to admit it (3), the fundamental reason has received different labels: attitude, belief, local practice, “experience,” and culture. Put simply, we as a profession do not yet emotionally accept coronary physiology to guide treatment. Call it “coronary psychology.”
↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
Dr. Johnson has received internal funding from the Weatherhead PET Center for Preventing and Reversing Atherosclerosis; has an institutional licensing and consulting agreement with Boston Scientific for the smart minimum fractional flow reserve algorithm; received significant institutional research support from St. Jude Medical (CONTRAST trial; NCT02184117) and Philips Volcano Corporation (DEFINE-FLOW trial; NCT02328820) for studies using intracoronary pressure and flow sensors; and has a patent pending on diagnostic methods for quantifying aortic stenosis and transcatheter aortic valve replacement physiology. Dr. Koo has received institutional research grant support from St. Jude Medical (Abbott) and Philips Volcano.
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