Painless ischemia

Painless ischemia - detection during instrumental examination methods (Holter ECG monitoring - HMECG, stress tests) of signs of myocardial ischemia, not accompanied by attacks of angina pectoris or their equivalent. It is believed that the absence of pain syndrome, despite the development of myocardial ischemia, is associated with an increased threshold of pain sensitivity, impaired endothelial function, defects in the autonomic innervation of the heart.

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Epidemiology of silent ischemia

The prevalence of silent ischemia is difficult to estimate and ranges from 2.5% in the general population to 43% in patients with various forms of coronary artery disease. Most researchers believe that silent ischemia is an independent (especially in patients with acute coronary syndrome) adverse risk factor for long-term prognosis, although the evidence base for this is still insufficient.

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Classification of silent ischemia

The most widely accepted classification is Cohn's, according to which three types of painless ischemia are distinguished: type 1 - in patients without any symptoms of angina, type 2 - in patients with painless myocardial ischemia after myocardial infarction, and type 3, when one patient has a combination of angina attacks and painless episodes of myocardial ischemia.

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Treatment of painless ischemia

The optimal management of patients with silent myocardial ischemia, both in terms of medication and invasive treatment, remains unresolved. Two studies have been completed comparing medication and invasive treatment in patients with types 2 and 3 silent ischemia. The ACIP study included patients without angina or with angina attacks that were well controlled by medication, with hemodynamically significant coronary artery stenosis detected by CAG, a positive ischemic stress test, and at least one episode of silent myocardial ischemia detected by 48-hour HMECG (i.e., patients with type 3 silent ischemia).

Patients who met the inclusion criteria were randomized into three groups: drug therapy aimed at relieving angina attacks (184 patients), drug therapy titrated until not only angina attacks but also silent episodes of myocardial ischemia on HMECG disappeared (182 patients), and a myocardial revascularization group (192 patients) in which CABG or PCI was performed depending on the anatomical features revealed by CAG. After 2 years of follow-up, mortality in the invasive treatment group was significantly lower than in the drug therapy group (6.6% in the angina relief group; 4.4% in the ischemia treatment group; 1.1% in the myocardial revascularization group). There was also a significant reduction in the incidence of the combined endpoint of death/myocardial infarction (12.1; 8.8 and 4.7%, respectively). During the study, 29% of patients who were initially randomized to drug treatment required invasive intervention. Patients in the invasive treatment group also frequently required rehospitalization due to exacerbation of coronary artery disease. Invasive treatment had a particularly favorable effect on the prognosis in patients with stenosis in the proximal LAD.

In 2008, data from the SWISSI study were published, comparing the effects of percutaneous coronary artery grafting and medical therapy in patients with a recent myocardial infarction who had silent myocardial ischemia (type 2 silent ischemia) during a stress test. The study included patients with one- and two-vessel coronary artery disease. If the inclusion criteria were met, patients were randomized to the PTCA group (96 people) and to the intensive medical therapy group (95 people) aimed at eliminating episodes of myocardial ischemia. All patients received acetylsalicylic acid (ASA) and statins. After 10.2 years of observation, the invasive treatment group showed a significant reduction in CVR by 81%, the incidence of nonfatal myocardial infarction by 69%, and the need for myocardial revascularization due to the development of angina symptoms by 52%. There was also a tendency toward a significant reduction in overall mortality by 58% (p = 0.08). Even after 10 years of observation, despite the more frequent combined nature of antianginal therapy in the drug treatment group, TBCA retained greater effectiveness in terms of relieving patients of ischemia (according to the data of the stress test at the end of observation), and increased exercise tolerance to a greater extent.

In the invasive treatment group, the initial LVEF was preserved, while in the drug therapy group, LVEF significantly decreased from 59.7 to 48.8% during the observation period. The survival curves began to diverge after 2 years of observation, and the divergence continued throughout the entire observation period. It should be emphasized that, given the time of the study (recruitment was carried out from 1991 to 1997), stents were not used in PCI in this study, and such drugs as clopidogrel, angiotensin-converting enzyme inhibitors (ACE inhibitors), high doses of stagins, and other drugs of standard modern therapy for patients after a heart attack were not used in the drug therapy group, so it is difficult to determine the applicability of these results to modern conditions. In contrast to observations in stable angina (including COURAGE), in the case of silent myocardial ischemia, both studies comparing PCI and drug therapy showed the advantage of the invasive approach in terms of not only reducing the severity of ischemia, but also the effect on hard endpoints (death, MI, need for repeat revascularization).

According to the latest recommendations of ACCF / SCAI / STS / AATS / AHA/ ASNC (2009), in case of silent ischemia, when choosing invasive and conservative tactics, it is necessary to focus on the data of non-invasive research methods, as well as the anatomical characteristics of the coronary bed lesion. The presence of a three-vessel lesion, lesion of the proximal segment of the LAD, the presence of high risk criteria for cardiovascular disease in non-invasive research methods - all this is the basis for choosing invasive treatment. And vice versa, in case of a single-vessel lesion not affecting the LAD, in combination with a low risk of cardiovascular disease according to stress tests, drug therapy is carried out.

Key points:

• Silent ischemia is an independent risk factor that worsens the long-term prognosis of patients.
• There are three types of painless ischemia, depending on the presence of a history of myocardial infarction and attacks of angina pectoris.
• Treatment of silent ischemia can be conservative (the goal of treatment is to eliminate ischemia) or invasive, in particular using PCI. The question of PCI should be decided individually for each patient, taking into account the data of noninvasive research methods, as well as the anatomical characteristics of the coronary lesion.
• The presence of three-vessel disease, damage to the proximal segment of the LAD, and the presence of high-risk criteria for cardiovascular disease using non-invasive research methods serve as the basis for choosing invasive treatment.
• PCI is not recommended in asymptomatic patients with single- or dual-vessel disease not involving the proximal LAD segment and low CV risk based on exercise testing.