A 52-year-old woman with newly diagnosed HER2-positive metastatic breast cancer is being evaluated for targeted therapy with trastuzumab. Which investigation is most appropriate to assess baseline cardiac function before initiating treatment?

Explanation

## Baseline Cardiac Assessment for HER2-Targeted Therapy **Key Point:** Trastuzumab and other HER2-targeted agents (pertuzumab, T-DM1) carry a risk of cardiotoxicity, particularly left ventricular dysfunction and heart failure. Baseline LVEF measurement is mandatory before initiating therapy. ### Why Echocardiography is the Gold Standard **High-Yield:** Transthoracic echocardiography (TTE) with measurement of left ventricular ejection fraction (LVEF) is the investigation of choice because it: - Directly quantifies systolic function (LVEF ≥50% is typically required before starting trastuzumab) - Detects early subclinical dysfunction - Allows serial monitoring during treatment - Is non-invasive, reproducible, and widely available **Clinical Pearl:** Current guidelines recommend baseline LVEF assessment and repeat echocardiography every 3 months during HER2-targeted therapy, or more frequently if dysfunction is detected. ### Comparison of Cardiac Investigations | Investigation | Utility in HER2-Therapy | Limitations | |---|---|---| | Transthoracic echo (LVEF) | Gold standard for baseline & monitoring | Operator-dependent, may have poor acoustic windows | | Chest X-ray | Detects gross cardiomegaly only | Insensitive for early dysfunction | | ECG with QTc | May show arrhythmias | Does not assess systolic function; trastuzumab cardiotoxicity is primarily systolic | | Cardiac biomarkers alone | Prognostic but not diagnostic | Cannot replace structural imaging; used as adjunct | **Mnemonic:** **ECHO FIRST** — **E**chocardiography, **C**ardiac function, **H**ER2 therapy baseline, **O**bjective LVEF, **F**irst test; **I**maging required, **R**epeat monitoring, **S**ystolic assessment, **T**argeted therapy cardiotoxicity. ### Additional Considerations - **Multigated acquisition (MUGA) scan** is an alternative if echo is technically inadequate, but TTE is preferred as first-line. - Baseline LVEF <50% is a relative contraindication; therapy may be deferred or alternative agents considered. - Cardio-oncology consultation is recommended for high-risk patients or those with pre-existing cardiac disease.