A 62-year-old woman with known coronary artery disease on long-acting nitrates presents with recurrent episodes of angina despite optimal medical therapy. Her resting ECG shows left ventricular hypertrophy. Which investigation is most appropriate to assess myocardial perfusion and guide further management?

Explanation

## Investigation of Choice for Myocardial Perfusion Assessment ### Role of Myocardial Perfusion Imaging **Key Point:** Myocardial perfusion imaging (MPI) using technetium-99m sestamibi SPECT is the investigation of choice for assessing the extent and severity of myocardial ischemia in patients with known coronary artery disease and recurrent angina despite medical therapy. ### Why Myocardial Perfusion Imaging? MPI provides: 1. **Spatial localization** of ischemic zones (anterior, inferior, lateral, septal) 2. **Quantification** of the extent of ischemia (percentage of left ventricle involved) 3. **Risk stratification** based on the size and severity of perfusion defects 4. **Prognostic information** to guide need for revascularization 5. **Functional assessment** of myocardial viability **High-Yield:** A large reversible perfusion defect (>10% of left ventricle) or multiple defects predict high risk and warrant coronary angiography and revascularization. ### Comparison of Investigations for Ischemia Assessment | Investigation | Sensitivity | Specificity | Utility | Limitation | |---|---|---|---|---| | **MPI (SPECT)** | 85–90% | 70–75% | Localization, risk stratification | Radiation exposure | | **Stress echo** | 80–85% | 85–90% | Wall motion, viability | Operator-dependent | | **Coronary CTA** | 95% | 90% | Anatomic detail | Radiation, contrast | | **Transthoracic echo (rest)** | Low | Moderate | LV function, structure | No ischemia assessment | | **Holter monitoring** | Low | Moderate | Arrhythmia detection | No ischemia assessment | ### Clinical Decision Algorithm ```mermaid flowchart TD A[Recurrent angina on medical therapy]:::outcome --> B{Need to assess ischemia extent?}:::decision B -->|Yes| C[Myocardial perfusion imaging]:::action C --> D{Large/multiple defects?}:::decision D -->|Yes| E[Coronary angiography + revascularization]:::action D -->|No| F[Optimize medical therapy]:::action B -->|No| G[Continue medical management]:::outcome ``` **Clinical Pearl:** In patients with abnormal baseline ECG (like LVH in this case), MPI is preferred over exercise stress testing because it provides spatial localization of ischemia independent of ECG changes. ### Why Other Investigations Are Suboptimal - **Coronary artery calcium scoring:** Assesses atherosclerotic burden, not current ischemia; does not guide acute management - **Transthoracic echocardiography:** Evaluates LV function and structure but does not assess myocardial perfusion or ischemia - **Holter monitoring:** Detects arrhythmias and silent ischemia but does not quantify or localize ischemic burden **Tip:** In patients with contraindications to nuclear imaging (pregnancy, severe renal disease), stress echocardiography or coronary CT angiography are alternatives.