A Phased Array Ultrasonic Testing (PAUT) transducer, typically 2-3 cm, provides a large depth of field with a small size which is ideal for viewing deep structures through small acoustic windows, such as between ribs in cardiac imaging. Operating at 2.0–7.5 MHz, phased array techniques rapidly steers the ultrasound beam, producing over 20 images per second with a resolution of 2-4 mm throughout the field of view.
A low-frequency phased array probe excels in cardiac ultrasound by providing four key views: subxiphoid, parasternal long axis, parasternal short axis, and apical 4-chamber. It can identify key structures such as the liver, atrium, and ventricles. These views are crucial for diagnosing conditions like pericardial effusion, which appears as an anechoic (black) area around the heart, and assessing left ventricular function through fractional shortening and E-point septal separation (EPSS). Additionally, it helps detect right heart strain, indicated by an enlarged right ventricle or McConnell sign.
Ultrasound with phased array probes plays a crucial role in managing cardiac arrest which can guide resuscitation efforts. It can identify reversible causes of cardiac arrest, such as tension pneumothorax, cardiac tamponade, or massive pulmonary embolism. During CPR, transthoracic echocardiography (TTE) helps assess and optimize chest compressions. In cases of pulseless electrical activity (PEA), ultrasound can indicate potential benefits from volume infusion or inotropic support. Moreover, it quickly demostrates a cardiac standstill, suggesting exhausted myocardial reserve. By integrating ultrasound into the resuscitation process without interrupting CPR, clinicians can enhance hemodynamic optimization and evaluate for complications like pneumothorax or organ dysfunction post-resuscitation.
