What is the best way to treat a patient with a stable coronary artery disease (CAD)? The cardiology community has been debating this question for decades and argues whether it is best to take a conservative or invasive approach.
The ISCHEMIA study (ischemia means that there is not enough oxygen in the heart muscle), a new study that was reported at the American Heart Association meeting in November, provides some answers. This study suggests that managing CAD with medication alone (the conservative approach) is just as safe and effective for most as the more invasive strategy of cardiac catheterization and opening the blocked artery.
Findings from the ISCHEMIA test
ISCHEMIA followed more than 5,000 patients with significant narrowing in one or more coronary arteries. Half of the patients were randomly selected for conservative treatment with optimal medical therapy (OMT) and lifestyle changes to treat risk factors such as high blood pressure and high cholesterol. The other half received OMT and also sent for heart catheterization (inserting a flexible catheter into the coronary arteries to look for narrowed or blocked coronary vessels). When blockages were found, these patients underwent placement of a small mesh tube, called a stent, to open the affected area. When blockages were too complex to place a stent, open heart surgery was performed.
The findings were surprising. Many cardiologists would have predicted that the invasive strategy would be superior to the conservative strategy. The group that received stents reported greater relief from angina or chest pain. But there was no significant difference between the two groups in terms of heart attack, death or hospitalization for worsening heart pain.
Proponents of the conservative approach claim that OMT is more logical than stent because it addresses all arteries in the heart, not just the small portion of constriction tackled by a stent that can cause angina, but may not pose a health risk.
Stents are still a good choice for unstable angina
Since their introduction in the 1980s, stents have been widely used in the treatment of CAD. Stents are effective in relieving angina in patients who continue to experience symptoms despite proper medication. Angina refers to the symptoms – usually chest pressure or tightness – that occur when the heart muscle does not get enough oxygen-rich blood.
Angina is a symptom of advanced atherosclerosis, a process of inflammation and plaque formation that leads to narrowing of blood vessels. If an atherosclerotic plaque ruptures, it can cause the formation of a blood clot, which seriously and suddenly blocks blood flow. Depending on the degree of obstruction and the artery, this can cause an abrupt worsening of angina, unstable angina, or the death of the heart muscle, causing a heart attack. Unstable angina occurs at rest, or with less and less effort.
Patients with unstable angina or a heart attack almost always require urgent heart catheterization and often stent placement.
Medications that are as effective as stents for stable angina
In contrast to unstable angina, patients with stable angina have more predictable, chronic symptoms that can be treated with medication. Stable angina worsens with exercise or sometimes with emotional stress and improves with rest. Reduction of stable angina includes improving the mismatch between oxygen supply and demand. This can be achieved by reducing demand or improving supply.
Demand can be reduced with OMT, including beta-blockers, which slow the heartbeat, or nitroglycerin, which reduces the work of the heart by relaxing the blood vessels. Statins and aspirin are another important part of OMT, as they help stop the progression of heart disease, reducing the risk of unstable angina or a heart attack. When medication fails, blood flow to the heart muscle can be increased by removing the blockage with a stent or bypassing the blockage with open heart surgery.
Many cardiologists have assumed that stents are effective not only in relieving symptoms but also in preventing future heart attacks, causing many to pursue early heart catheterisations for their patients with stable angina. However, the ISCHEMIA study suggests that drugs are just as good at preventing heart attacks and death in stable patients.
This is welcome news for patients previously insisted on cardiac catheterization and stent placement for stable angina. It now seems clear that these patients can be treated safely with medication only, while avoiding the risk and inconvenience of the procedure, not to mention reducing healthcare costs.
Optimal medical therapy safe and effective for most with coronary artery disease
ISCHEMIA is not the first study to show that OMT is a safe and effective alternative to stent placement. But it is the most influential because of the careful design, the large number of patients and the comparison of the latest stents and the most current medical treatments.
So how can patients with stable coronary artery disease be treated best? A safe and effective long-term strategy for most is to start with medication and a healthy lifestyle. For those who are restricted by angina, an invasive procedure is suitable for symptom control. Stents relieve angina, but they do not prevent heart attacks or death.