Table 5.1 Summary: Ventricular septal defects

The most common congenital cardiac defect in the horse

Usually in membranous portion of the interventricular septum, just ventral to the aortic root

Typically pansystolic, harsh, grade 3-6, plateau-type murmur, PMI right apex

VSDs which may be compatible with athletic performance

No other clinical signs

Normal resting heart rate

Normal pulse quality

No abnormal arrhythmias

Normal intensity heart sounds

No volume overload

VSD<2.Scm diameter

Jet>4.0-4.5 m/sec on CW Doppler

Normal PA diameter

No excessive tachycardia after exercise

Poor prognostic indicators

Other clinical signs including tachypnoea, jugular distension, jugular pulsation, ventral oedema

Raised resting heart rate

Brisk or weak arterial pulse quality

Abnormal arrhythmias such as AF or VPCs

Loud S2 or S3 heart sounds

Volume overload

VSD>2.5 cm, subpulmonic or muscular

Jet <4.0 mlsec

Dilated PA

Poor exercise tolerance