Stable Ischemic Heart Disease (SIHD) is also called Stable Coronary Artery Disease.
In SIHD the cholesterol buildup in the heart arteries narrows the arteries involved and restricts blood flow through the arteries. At rest there is a baseline amount of blood flowing through the heart blood vessels to supply the heart muscle. With exercise the amount blood flowing through the heart arteries increases up to four times the baseline amount.
At rest in Stable Ischemic Heart Disease there is enough blood flow for the heart muscle. But when the heart has to work harder, the cholesterol buildup that narrows an artery limits the amount of extra blood that can flow through to the heart muscle.
So the heart muscle can’t get enough blood to function efficiently and symptoms occur. The symptom might be chest pain or shortness of breath with exercise or with emotional stress.
There are then three things we can do to increase blood flow to heart muscle. We can bypass the artery narrowing with bypass surgery (CABG). We can open up the narrowed segment of the artery with balloon angioplasty/stent (called a Percutaneous Intervention [PCI]. And finally we can give medicines that can help the heart muscle function efficiently and help prevent further buildup. This is called Optimal Medical Therapy (OMT) in the European guidelines.
There are three arteries that supply blood to the heart muscle: the right coronary artery (RCA), the left anterior descending artery(LAD), and the left circumflex artery (LCA). The left anterior descending and the left circumflex are actually branches of another very short artery called the left main artery.
If a person has severe cholesterol buildup throughout all his coronary arteries, then he can be at increased risk of dying. And increasing blood flow by bypass surgery or PCI can markedly decrease his risk of death.
The 2010 European “Guidelines on Myocardial Revascularization” give clear recommendations on when and how to treat Stable Ischemic Heart Disease (SIHD).
To lessen a person’s risk of death, the Guidelines recommend revascularization in SIHD in patients who have 50% narrowing of the left main coronary artery, a 50% narrowing of the proximal (meaning near the beginning of the artery) LAD, 2 or 3 vessel disease with impaired left ventricular function (usually meaning a decreased ejection fraction measured on echo or other imaging study), proven large area of ischema (> 10% of the left ventricle on an imaging study), a single remaining patent coronary artery with > 50% narrowing.
For a clear graphic summary of the above, see Table 8 on p 2513 (13 on the pdf) of the European guidelines at: http://www.escardio.org/guidelines-surveys/esc-guidelines/GuidelinesDocuments/guidelines-revasc-FT.pdf.
Usually in the above cases coronary artery bypass graft surgery will be recommended rather than angioplasty stent.
For less severe stable coronary artery disease with symptoms not adequately controlled with medicine, PCI or CABG may be appropriate. Both have advantages and disadvantages.
In the December 12 post I’ll go over how we can determine the risk of bypass surgery and angioplasty/stent using risk scores.