🔬 Transthoracic Echocardiography

Transthoracic Echocardiography (TTE) is a non-invasive, ultrasound-based investigation used to assess cardiac structure and function. It provides real-time images of the heart chambers, valves, and blood flow. It is the primary tool for diagnosing heart failure and valvular heart disease in both inpatient and outpatient UK settings.

Common indications include investigation of heart failure symptoms (oedema, orthopnoea), assessment of heart murmurs, and evaluation of hypertension or chest pain. It is used to screen for cardiomyopathy in families, to look for a source of embolism in stroke (e.g., thrombus or PFO), and to assess the heart after a myocardial infarction. It is also indicated in patients with unexplained syncope or palpitations.

TTE uses high-frequency sound waves emitted from a transducer placed on the chest wall. The patient is usually positioned in the left lateral decubitus position to bring the heart closer to the chest wall. The sonographer obtains images from several 'windows': parasternal, apical, subcostal, and suprasternal. It is non-invasive, uses no radiation, and can be performed at the bedside.

A normal TTE reveals a Left Ventricular Ejection Fraction (LVEF) of typically 55-70%. All চার chambers should be of normal size, and the heart valves should open and close fully without significant stenosis or regurgitation. The pericardium should be thin with no fluid. There should be 'global' contraction with no regional wall motion abnormalities, and normal diastolic filling patterns.

The interpretation involves both visual assessment and quantitative measurements. The EF is often calculated using Simpson's biplane method. Doppler ultrasound is used to measure the 'velocity' of blood flow across valves; high velocities indicate stenosis. Diastolic function is assessed by looking at the filling patterns of the left ventricle. All findings must be contextualised with the patient’s clinical status and ECG.

Abnormal findings include a reduced Ejection Fraction (EF <50%), which indicates heart failure. Valvular abnormalities include stenosis (e.g., calcified aortic valve with reduced opening) or regurgitation (e.g., mitral valve prolapse). Regional wall motion abnormalities (RWMA) suggest previous or current myocardial infarction. Pericardial effusion, thickened myocardium (as in HOCM), or dilated chambers are also key pathological indicators.

TTE is the most common cardiac imaging modality in the UK. It is fundamental in the diagnosis and staging of heart failure, guiding the initiation of ACE inhibitors and beta-blockers. It is used to monitor patients with known valvular disease to determine the timing of surgical intervention. In the acute setting, it can identify life-threatening conditions like cardiac tamponade or acute heart failure.

Underestimating the severity of valvular disease due to poor alignment of the Doppler beam is a common technical pitfall. Over-reliance on visual 'eyeballing' of the EF can lead to inaccuracy compared to formal volumetric measurements. It can also be difficult to distinguish between acute and chronic changes (e.g., RV dilatation) without clinical context or previous scans.

TTE is highly operator-dependent; the quality of the report depends on the skill of the sonographer. Image quality can be significantly limited by 'poor acoustic windows' in patients with obesity, chronic obstructive pulmonary disease (COPD due to hyperinflated lungs), or those who cannot lie on their left side. It cannot directly visualise the coronary arteries (unlike CT coronary angiography).

Remember the 'Big 3' measurements: LVEF (Left Ventricular Ejection Fraction), Valve areas, and Chamber sizes. Be aware that a 'Normal EF' does not rule out heart failure (HFpEF - Heart Failure with Preserved Ejection Fraction). Note that TTE is less sensitive than Transoesophageal Echo (TOE) for small vegetations in endocarditis.