Coronary artery disease (CAD) or ischaemic heart disease refers to the long-standing narrowing or blockage of one or more of the arteries sitting on the heart muscle that can result in less blood flow to the heart muscle. It is a chronic disease with a broad range of potential associated symptoms that are referred to as “stable” if symptoms are not present, or not changing in frequency or intensity over a period of time, as opposed to “unstable” symptoms which suggest an acute change in degree of narrowing and require prompt medial assessment and treatment.  Stable CAD is also associated with increased risk of potential adverse clinical outcomes, including future heart attack, heart failure, arrhythmia (irregular heart rhythm) and even sudden death. Historically, there were essentially three ways to reduce or avoid the risk of adverse events from stable CAD; the first is through lifestyle and risk factor modifications; the second is with medical therapy; the third is with “revascularisation”, in other words improving blood flow to one or more narrow or blocked coronary arteries via implantation of coronary artery stents, or via open heart surgery with coronary artery bypass surgery. However, results from large clinical trials in the last few years have supported the use of medical therapy rather than revascularisation with stents or bypass surgery as the most effective and appropriate initial management approach for most patients with stable CAD. A recently published paper in the Journal of the American College of Cardiology eloquently outlined the principles and supporting evidence for the evaluation and management of patients with stable CAD, with key points detailed below:

• Observational studies have shown that patients with stable CAD usually experience no or mild chest pain, also referred to as “angina”. The risk for major adverse cardiovascular outcomes is relatively low in patients with CAD and stable angina. In this setting, modification of risk factors with medical and lifestyle therapy is always recommended.  These risk factors include smoking, being overweight, high blood pressure, high cholesterol and diabetes. Coronary revascularisation with stents or bypass surgery only needs to be considered if optimal medical therapy is not effective. 
• Coronary revascularisation with stents or bypass surgery should be considered for specific patients with severe symptoms despite taking guideline recommended optimal medical therapy, or patients with narrowings in critical parts of the coronary arteries, such as the left main coronary artery, which If blocked, puts the blood supply of two thirds of the heart muscle at risk and is therefore associated with increased risk for adverse cardiac events. 
• Evidence suggests that most patients with stable angina will have similar outcomes and resolution of symptoms with either medical therapy or revascularisation. The randomised COURAGE (Clinical Outcomes Utilizing Revascularisation and Aggressive Drug Evaluation) trial published in 2007 showed that improved quality of life can be achieved with both optimal medical therapy alone or combined with percutaneous coronary intervention (stenting), meaning that medical therapy alone is not an inferior approach, and much safer as it does not subject patients to potential complications associated with invasive procedures. 
• The ISCHEMIA (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches) trial enrolled patients with stable CAD and moderate to severe ischaemia, in other words moderate to severe impairment of blood flow to the heart muscle when the heart is under stress. Patients were randomised to receive an invasive strategy of optimal medical therapy plus coronary angiogram and coronary revascularisation, if possible, or a conservative strategy of optimal medical therapy alone, with revascularisation reserved for treatment failure.  The primary endpoint was myocardial infarction (heart attack), cardiovascular death, hospitalisation for unstable angina, heart failure, or resuscitated cardiac arrest. The results were published in 2020 and showed no significant between-group difference for the primary endpoint or for the secondary endpoints of cardiac mortality or all-cause mortality, heart attack, cardiac arrest, or stroke. This means that a primary invasive strategy including angiography and revascularisation does not necessarily lead to better outcomes than medications alone in patients with stable CAD, even in patients with more severe ischaemia.
• A number of studies have shown that revascularisation with stenting can reduce ischaemic burden in patients with stable CAD, in other words, stenting can improve blood flow to the heart muscle. However, importantly, this improvement in blood flow has not been shown to be associated with an improvement in survival or reduced risk for recurrent heart attacks. However, revascularisation for patients with stable CAD and narrowings in critical parts of the coronary circulation is still beneficial. This includes narrowings in the left main coronary artery, coronary heart narrowings in all three main coronary arteries, and double vessel narrowings that include the proximal (top) of the left anterior descending coronary artery (which is the artery that runs down the front of the heart muscle). Studies have also shown revascularisation to be more effective than medications alone in patients with cardiomyopathy (weak heart muscle pump function), as well as and diabetes with multivessel coronary heart disease. 

So overall, extensive data now published over many years from large clinical trials consistently support the use of optimal medical therapy rather than revascularisation with stents or bypass surgery for initial management of the majority of patients with stable CAD, in other words those with blocked or narrow arteries that have minimal or stable symptoms. Revascularisation with stents or bypass surgery in patients with stable CAD only needs to be considered for specific patients with severe symptoms despite optimal medical therapy or patients with particularly severe anatomical disease such as left main stenosis, which increase the risk for adverse events. Please note however, that the aforementioned information does not apply to patients with ‘unstable’ or escalating symptoms, or in patients who present to hospital with chest pain caused by an acute heart attack, where revascularisation (usually with stenting) of an acutely blocked or narrowed artery unequivocally leads to better outcomes in most instances.

Reference:

Evaluation and Management of Patients With Stable Angina: Beyond the Ischemia Paradigm: J Am Coll Cardiol. 2020, Nov 76 (19) 2252–2266. R Ferraro, J Latina, A Alfaddagh et al.