Abstract

Echocardiography is a unique non-invasive application of ultrasound for imaging of living heart. It is based on detection of echoes produced by a beam of ultrasound pulses transmitted into the heart. Conventional echocardiographic modalities include two-dimensional (2D), M-mode and Doppler modes. M-mode is the first ultrasound modality used in which the ultrasound beams are aimed manually at selected cardiac structures to give a graphic recording of their positions and movements. M-mode recordings permit quantitative measurement of cardiac dimensions and detailed analysis of complex motion patterns depending on transducer angulation. It facilitates analysis of time relationships with other physiological variables such as echocardiographic, heart sounds, and pulse tracings, which can be recorded simultaneously. However, it cannot be used to measure velocity, the direction or type of the blood flow but can be combined with contrast or colour-coded Doppler studies for accurate timing of flow events. Variations in M-mode echocardiographic parameters with breed, age, sex and body weight occurs and need to be kept in mind while interpreting the findings. Its variables are usually subjected to change and needs experienced sonologist to diagnose any condition. The present review covers the M-mode echocardiographic developmental history in general and its diagnostic role for dogs in particular.

Key words: M-mode, echocardiography, dogs, ultrasound.