A 52-year-old man with hypertension presents with palpitations and dyspnea. On examination, an irregular pulse is noted. A 12-lead ECG shows absence of P waves and an irregularly irregular rhythm with a ventricular rate of 110 bpm. Which investigation is most appropriate to assess the structural substrate and guide long-term management?

## Clinical Context The ECG findings — absent P waves, irregularly irregular rhythm, and rapid ventricular response — are diagnostic of atrial fibrillation (AF). The clinical question shifts from diagnosis (already established by ECG) to assessment of the structural heart and risk stratification. ## Why Transthoracic Echocardiography Is Correct **Key Point:** Transthoracic echocardiography (TTE) is the first-line imaging modality in newly diagnosed AF to: - Assess left ventricular function (ejection fraction, wall motion) - Evaluate left atrial size and function - Detect underlying structural heart disease (valvular disease, cardiomyopathy, LV hypertrophy) - Screen for thrombus in the left atrial appendage (LAA) - Guide anticoagulation and rate-control strategy **High-Yield:** TTE is recommended by ACC/AHA guidelines as part of the initial evaluation of all patients with newly diagnosed AF to identify reversible causes and stratify stroke/heart failure risk. **Clinical Pearl:** In this patient with hypertension and new-onset AF, TTE will likely show left ventricular hypertrophy and possibly impaired diastolic function — common substrates for hypertension-related AF. ## Why Other Options Are Incorrect | Investigation | Timing / Indication | | --- | --- | | **Cardiac MRI** | Reserved for specific indications: suspected infiltrative/inflammatory disease, arrhythmogenic right ventricular cardiomyopathy, or when TTE is inconclusive. Not first-line for routine AF evaluation. | | **Coronary angiography** | Indicated only if the patient has symptoms or signs of acute coronary syndrome, or if non-invasive stress testing is abnormal. Not part of routine AF workup unless ischemia is suspected. | | **Electrophysiology study** | Performed for rhythm control strategy (ablation) after medical therapy failure, or for specific arrhythmia mapping. Not indicated for initial structural assessment in newly diagnosed AF. | ## Investigation Algorithm for New-Onset AF ```mermaid flowchart TD A[New-onset Atrial Fibrillation]:::outcome --> B[12-lead ECG]:::action B --> C[Diagnosis confirmed]:::outcome C --> D[Transthoracic Echocardiography]:::action D --> E{Structural disease detected?}:::decision E -->|Yes: HF, valvular disease| F[Optimize medical therapy]:::action E -->|No: structurally normal| G[Assess stroke risk - CHA₂DS₂-VASc]:::action G --> H[Anticoagulation + Rate control]:::action H --> I{Symptom control achieved?}:::decision I -->|No| J[Consider rhythm control / Ablation]:::action I -->|Yes| K[Long-term follow-up]:::outcome ```