## Rationale for Baseline Cardiac Assessment in HER2-Targeted Therapy **Key Point:** Trastuzumab is a monoclonal antibody against HER2 that carries a significant risk of cardiotoxicity (dilated cardiomyopathy and congestive heart failure), particularly when combined with anthracyclines. Baseline and serial cardiac monitoring is mandatory before and during therapy. ### Why Transthoracic Echocardiography is the Investigation of Choice **High-Yield:** Transthoracic echocardiography (TTE) is the standard, non-invasive, reproducible, and cost-effective method to measure LVEF at baseline and during treatment. It is recommended by ASCO, NCCN, and ESMO guidelines as the first-line investigation for cardiac risk stratification in HER2-positive breast cancer patients. **Clinical Pearl:** LVEF must be ≥50% (or ≥55% in some protocols) before initiating trastuzumab. Serial echocardiography is performed every 3 months during therapy and at 6 months post-completion to detect asymptomatic decline in function. ### Comparison of Cardiac Investigations | Investigation | Role | Limitations | |---|---|---| | **Transthoracic echocardiography** | First-line baseline and serial monitoring | Operator-dependent; limited acoustic windows in some patients | | Cardiac MRI | Gold standard for LVEF; superior image quality | Expensive, time-consuming, not routine for screening | | Coronary angiography | Invasive; reserved for symptomatic CAD | Not indicated for asymptomatic risk assessment | | Biomarkers (troponin, BNP) | Supportive; detect myocardial injury/stress | Lack specificity; not sufficient alone for LVEF assessment | **Mnemonic: HER2 Cardiotoxicity Screening = **ECHO** (Echocardiography, Cardiac, Hazard, Ongoing)** **Tip:** If TTE is technically inadequate (poor acoustic windows), cardiac MRI or gated SPECT can be used as alternatives, but TTE remains first-line.
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