By Deborah J. DeWaay, MD, FACP
Associate Professor, Medical University of South Carolina, Charleston, SC
SYNOPSIS: Patients with vasospastic angina and a type II myocardial infarction have a worse prognosis than previous believed.
SOURCE: Matsue Y, et al. Clinical Features and Prognosis of Type 2 Myocardial Infarction in Vasospastic Angina. Am J Med 2015; 128(4):389-395
Transient spastic narrowing of the coronary vasculature can lead to chest pain and is called vasospastic angina. Although, some patients will have sequela that include acute myocardial infarction and sudden death, most patients have a good prognosis overall. In 2007, a group of leading cardiology associations classified five types of myocardial infarctions. A type II myocardial infarction (MI) was defined as a troponin I that is greater than the 99th percentile and vasospastic angina. Extensive research has not been done on characterizing this type of MI. The authors of this paper did a retrospective analysis of patients admitted to their institution for vasospastic angina in order to better characterize patients with vasospastic angina and type II MIs and understand their prognosis.
All patients (n=512) admitted for chest pain secondary to vasospastic angina over an eight-year period at the Kameda Medical Center in Japan were reviewed retrospectively for this study. The inclusion criteria were: having an initial troponin on admission and a definite diagnosis of vasospastic angina per the Guidelines for Diagnosis and Treatment of Patients with Vasospastic Angina for Japanese Circulation Society. Patients with a previous admission for heart failure, coronary revascularization, advanced renal disease (glomerulofiltration rate < 30mL/min/1.73m2 or ESRD) or a diagnosis of Takotsubo cardiomyopathy were excluded. Patients who received coronary revascularization during the hospitalization were also excluded. All patients received an echocardiogram during their admission. Ultimately, 171 patients were included in this study.
Patients were assessed for vasospastic angina with an acetylcholine provocation test during their coronary angiography. The hospital where this study was performed used several different types of troponin I assays over the eight years. Authors used the 99th percentile in all of the different assays as a cut off for a “positive” test. On angiography, organic coronary stenosis was defined as more than 50% luminal narrowing of the artery. A retrospective chart review was performed of the hospital stay and follow-up data was obtained from the outpatient clinic associated with the hospital. The authors calculated a clinical risk score to estimate prognosis of vasospastic angina, which was defined using a Japanese national registry (Japanese Coronary Spasm Association – JCSA). The endpoints of this study were all-cause death (1°), non-fatal MI (1°) and all-cause mortality (2°). The median follow-up was 4.4 years.
All of the baseline patient characteristics were the same in both groups, except the group without type II MIs were older when compared to the group without MI (64.8 years vs. 60.0 years; p = .043). There was no significant difference between the groups with respect to rates of diabetes, hypertension, dyslipidemia, and smoking. 93% of patients had a definitive acetylcholine provocation test. 95.9% of patients were prescribed calcium channel blockers for treatment. Six patients were treated with beta-blockers. 89.5% of patients had ST-segment change during spontaneous chest pain.
Using the JCSA risk score, 45.6% of all patients were low risk, 40.9% were intermediate risk, and 13.5% were high risk. In contrast to the entire patient group, 16.7% of the type II MI patients were low risk, 27.1% were intermediate risk, and 38.5% were high risk. The patients with Type II MI had a higher average JCSA risk score when compared to the non-MI group (3.5 vs 2; p=.003).
In this study, 32% of patients admitted for vasospastic angina met criteria for a type II MI. Patients with a type II MI were more likely than those that did not to have a nonfatal MI or death during the study period (26.2% vs. 9.3%; p =.008). The overall five-year survival for patients with vasospastic angina is in the ninety percentile. In this study, the five-year overall survival for the group with a type II MI was 84.7% and the combined end-point free survival was 71.7%. The mechanism for type II MI in this group was not evaluated in this study. Other early invasive studies have shown that prognosis is poorer when there is worsening endothelial dysfunction even in patients without coronary artery disease. In addition, microvascular dysfunction is an independent predictor of a poorer prognosis. The authors speculate that this subgroup may have severe smooth muscle and endothelial cell dysfunction and may have worsening microvascular dysfunction that cannot be assessed on an angiogram.
This study has several limitations. First, it is a retrospective, single-institution study that was done in Japan, so generalizability may be limited. However, vasospastic angina and type II MIs are less common, so the findings of this study are still relevant. Second, the number of patients and events was small. Third, the follow-up time on the patients was short.
Although the generalizability of this study is questionable, it is still an important study for hospitalists to review. The common thought process is that vasospastic angina is a relatively benign disease, even if it causes a type II myocardial infarction. The treatment of this type of MI does not fall into the common treatment algorithm and the prognosis for this illness has not been well defined. This study serves as an important review of the illness and a reminder to counsel patients on their risks appropriately. The patients in this study with type II MIs were younger and, therefore, physicians may be more inclined to overestimate their prognosis. It is important that patients with vasospastic angina, especially if they have had a type II MI, be counseled that this is not a benign illness and that close follow-up with risk factor modification is important.