By: Geoffrey Modest
The American College of Cardiology and American Heart Association updated their guidelines on diagnosis and management of stable ischemic heart disease (SIHD) — see doi:10.1016/j.jacc.2014.07.017.
Main points:
Diagnosis of SIHD (new section on invasive testing recommendations):
–Coronary angiography is useful in patients with presumed SIHD but unacceptable ischemic symptoms despite optimal guideline-directed medical therapy (class 1 recommendation, level C evidence)
–Coronary angio is reasonable in those with clinical characteristics and results of non-invasive testing which suggest a likelihood of severe ischemic heart disease (eg, long-standing diabetes with end-organ damage, severe periph arterial dz such as AAA, previous chest irradiation, or patients with typical angina assoc with transient heart failure, pulm edema or syncope) and are amenable to/are candidates for revascularization (class IIa, level of evidence C: ie, they are in favor of it but there is significant divergence of opinion)
–Coronary angio is reasonable in those with suspected SIHD who cannot do noninvasive testing or have nondiagnostic tests, and the results have “a high likelihood that the findings will result in important changes to therapy” (class IIa, level of evidence C)
–Might consider coronary angio if stress test of acceptable quality, does not show CAD, but the clinical suspicion is still very high and results would lead to changes in therapy (class IIb, level of evidence C)
–These guidelines do not address utility of angio in patients with heart failure/reduced ejection fraction, unexplained sudden death/sustained ventric arrhythmia, preop cardiovasc eval.
Note: there are no high-quality studies which randomize people to cath/no cath and look at outcomes (trials so far have been revasc vs med therapy after caths were done). there is one ongoing study in the works (ISCHEMIA trial). They also note that cath results may not correlate with symptoms (some with >70% stenosis do not have significantly decreased coronary blood flow, and some with less do have hemodynamically significant lesions). Newer studies (intravasc ultrasound, optical coherence tomography/measurements of fractional flow reserve) may correlate better. and there is a 1.5% risk of significant complications with cath, highest in those >70yo and with more marked functional impairment. Also, there are huge regional variations in the use of cath, though overall 45% did not detect clinically significant disease in the large ACC registry. Even in those with positive noninvasive stress tests, only 41% had significant CAD on cath. Esp an issue in women (more likely to have microvascular disease and negative cath)
Treatment of SIHD:
–Modified prior recommendation on chelation therapy (eg EDTA infusion): in 2012, was “no benefit”. now usefulness is “uncertain”. Studies are mixed. concept is that there are some heavy metals (eg cadmium, in cigarette smoke) that are assoc with cardiovasc risk.
–They review the literature on enhanced external counterpulsation in those with refractory angina and do not change their recommendation that it “may be considered”
–Revascularization. Modified recommendation that (1) Heart Team approach is recommended if pt has diabetes or complex multivessel CAD; (2) “generally recommend” CABG over PCI to improve survival if diabetes or multivessel CAD, esp if can use LIMA graft. They cite the 2010 SYNTAX trial, an RCT of CABG vs a drug-eluting stent (DES), finding worse outcomes with the stent (higher major cardiac/cerebrovasc adverse events, MI rate, repeat revascularization, even after 5 years of followup — predominantly in those with worse lesion location, severity, and extent of stenoses — the SYNTAX score). The data on left main disease was complex: overall similar outcomes between CABG and DES. 45% had complex disease that prevented randomization and most went directly to CABG. most who were randomized, however, had low SYNTAX score, and after 3 years (subgroup analysis) did better with DES. Those with high SYNTAX score did much better with CABG. bottom line: carefully selected pts with left main disease do well with PCI in this and 2 other studies. for diabetes, the FREEDOM study in 2012 found a clinical benefit to CABG over DES. other studies somewhat mixed (none finding advantage to PCI, and those not finding significant benefit of CABG did find very-close-to-significant advantage)
As per most guidelines these days, the majority of people involved in writing these guidelines (23/42) had some pharmaceutical/medical supply relationship.
So, to me these guidelines are pretty reasonable. cardiac caths have been historically overused (eg the big hospital database that less than half the patients actually had CAD), and these current guidelines hone in on those with a higher probability of dangerous CAD lesions, with a focus on doing caths only if the results would significantly impact therapy. Unfortunately, this update did not evaluate or stress the importance of high-quality medical therapy, which often is as good as invasive approaches and has the added (and very important benefit) of decreasing the likelihood of progression of new lesions, by emphasizing the longterm lifestyle changes (diet, exercise, weight control) and meds (statins, etc). Also, bear in mind that cath is a static anatomic assessment and does not give much insight into the development of acute coronary syndromes: 78-97% of culprit lesions in developing ACS are less than 75% stenotic and half are less than 50% (ie, the issue seems to be that thrombotic coronary occlusion occurs mostly in smaller lesions with lipid-rich core and a thin fibrous layer of intimal tissue covering a necrotic core, not the large more occlusive lesions which lead to anginal symptoms on exertion (see doi:10.1056/NEJMoa1002358).