Case 3

Published on 02/03/2015 by admin

Filed under Internal Medicine

Last modified 22/04/2025

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Case 3

A 60-year-old woman was referred for SPECT MPI for evaluation of chest pain. The chest pain description was consistent with atypical angina. Her coronary risk factors included hyperlipidemia, hypertension, and a family history of premature coronary artery disease (CAD).

Resting ECG was normal.

According to published appropriateness criteria, stress MPI would be appropriate (median score = 7) in a patient with chest pain, an interpretable ECG, and an intermediate pretest probability of CAD based on presenting symptoms, age, and gender.

Exercise Data

She exercised to a maximal workload of 10 METs, achieving a peak heart rate of 150 beats/min (94% of maximum age-predicted heart rate). No chest pain was reported during exercise, and the blood pressure and ECG responses were normal.

SPECT Images

SPECT MPI demonstrated normal uniform uptake of ^99mTc-sestamibi in all myocardial regions. Gated SPECT demonstrated normal myocardial systolic thickening in all myocardial regions, with a computed left ventricular ejection fraction (LVEF) of 63%.

Clinical Questions

1. Would she benefit from coronary revascularization? No. The absence of inducible ischemia at an adequate exercise workload and the presence of normal left ventricular function suggest a low short-term risk for myocardial infarction or cardiac death.

2. Does she have coronary artery disease, and would she benefit from aggressive risk-factor modification? At this point, we cannot answer this question. The finding of normal myocardial perfusion on MPI does not exclude the presence of nonobstructive coronary atherosclerosis.

Framingham Risk Score

Age: 60
Gender: Female
Total Cholesterol: 210 mg/dL
HDL Cholesterol: 45 mg/dL
Smoker: No
Systolic BP: 155 mm Hg
BP Medication: Yes
Risk Score: 6% over 10 years

Based on her age, gender, lipid values, blood pressure, and smoking status, her calculated Framingham Risk Score is 6% (10-year risk). This places her in a low-risk category. Primary prevention guidelines would apply.

Coronary Calcium Score (CCS)

Coronary calcium scoring (CCS) was performed to further assess her risk for coronary events. Calcified plaque was detected in the left main (15), LAD (314), left circumflex (320), and RCA (353), with a total CCS of 1002 (>90th percentile for age and gender). These findings confirm the presence of extensive coronary atherosclerosis and suggest that she is at increased long-term risk for cardiac events.

Observation studies have shown that over 50% of patients with normal MPI studies have evidence of clinically significant coronary atherosclerosis (CCS > 100). Therefore, CCS may be used to further define long-term coronary risk in patients with normal MPI results.

However, CCS is not appropriate following a normal MPI study in patients who already qualify for aggressive risk-factor modification, such as those with:

1. Known coronary artery disease (prior MI, PCI, or CABG)

2. Coronary heart disease risk equivalents (carotid disease, peripheral arterial disease, abdominal aortic aneurysm, diabetes)

Patient Management

Based on the normal MPI results and the markedly elevated CCS, aggressive medical therapy would be appropriate (according to secondary prevention guidelines). However, the managing cardiologist was concerned that the normal SPECT MPI results might represent a “false-negative” study due to balanced myocardial ischemia. Coronary angiography was therefore performed. The angiogram demonstrated mild diffuse coronary artery disease (<20% stenoses in all three major coronary arteries). Thus, the coronary angiogram added no additional information in this case. The angiogram simply confirmed the findings of mild diffuse CAD (already documented on CCS) and the absence of flow-limiting stenosis (already documented on MPI).

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