Ultrasound Basic Echocardiography for the Internist Carol Gruver, MD, FACC UT Erlanger Cardiology Mechanical wave of compression and rarefaction Requires a medium for transmission Ultrasound frequency above audible range for humans (>20,000 Hz) For adult cardiac imaging, 4 7 MHz ultrasound waves Sound created and detected in the transducer Increasing signal frequency increases image resolution 5 MHz has twice the resolution of 2.5 MHz Attenuation increases with increasing frequency, so signal cannot penetrate as far Mechanical (sector) transducer Piezoelectric crystal moved through a sector sweep Linear Phased Array transducer Elements activated at different times Allows US beam to be steered 1
Three Basic Modes to Image the Heart Two-dimensional imaging Two dimensional (2D) imaging M mode imaging Doppler imaging Mainstay of echocardiographic imaging Multiple pulses sent out along adjacent scan lines Sector formed by multiple scan lines Process repeated multiple times for live imaging Speed of US in tissue & rapid signal processing allow for real time imaging M-mode Imaging Doppler Effect Multiple pulses sent out along a single scan line (1D view) A sound wave reflected from a moving object changes its frequency proportional to the velocity of the object High temporal and spatial resolution Estimates of blood flow velocity can be made by comparing the frequency change between transmitted and reflected sound waves V = (F D X C) / (2F O X Cosθ) Where F D is the Doppler shift; F O is the original frequency V is the velocity of blood; C is the speed of sound in tissues Continuous wave Doppler Color flow Mapping Pulsed wave Doppler Tissue Doppler imaging 2
Indications for Transthoracic Echo Symptoms potentially due to suspected cardiac etiology Assessment of known or suspected congenital heart disease Evaluation of suspected complications of myocardial infarction/ischemia Initial evaluation of murmur when reasonable suspicion of valvular or SHD Initial evaluation of prosthetic valve to establish baseline after placement Initial evaluation of suspected endocarditis with positive blood cultures or new Evaluation of suspected cardiac mass or tumor Evaluation of pericardial conditions Initial evaluation of known or suspected cardiomyopathy Known or suspected Marfan disease for evaluation of aortic root and mitral valve (J Am Soc Echocardiogr 2011;24:229 67.) 3
Cardiac Tamponade IVC in Tamponade 4
McConnell s Sign 5
Indications for Stress Echocardiography Initial evaluation of chest pain syndrome or angina equivalent Intermediate pre test probability of CAD, ECG uninterpretable or unable to exercise Worsening symptoms: abnormal catheterization or abnormal prior stress imaging study Re evaluation of medically managed patients Chest pain syndrome or angina equivalent, prior test result Coronary artery stenosis of unclear significance Preoperative evaluation for non cardiac surgery, high risk non emergent surgery Poor exercise tolerance (< 4 METs) Risk assessment post revascularization (PCI or CAB), symptomatic Evaluation of chest pain syndrome, not in the early post procedure period Ischemic cardiomyopathy, assessment of viability/ischemia Known CAD at catheterization, patient eligible for revascularization Valvular stenosis Evaluation of equivocal aortic stenosis, evidence of low cardiac output, use of dobutamine Use of contrast with stress echo Selective use of contrast, 2 or more contiguous segments are not seen on non contrast images (J Am Soc Echocardiogr 2011;24:229 67.) Dobutamine Stress Echo 6
Dobutamine Stress Echo D GO BIG BLUE 7