Synergy of Contraction

Synergy of contraction refers to the normal synchronous, coordinated and efficient contractile process involving all chambers of the heart yielding optimal ejection of fluid. The normal left ventricle ejects about 60% of its end-diastolic volume and the normal right ventricle ejects about 50% of its end-diastolic volume.

How do changes in synergy of contraction change cardiac performance?

Abnormalities of synergy of contraction (producing dyssynergy of contraction) are typically referring to the development of arrhythmias (dysrhythmias). Arrhythmias may result in disorganized and non-synchronous contraction of the segments of the heart. In this setting, arrhythmias may markedly reduce stroke volume, in fact to the point of a negligible stroke volume. Most arrhythmias are intermittent and infrequent and so may have no demonstrable effect on cardiac output. Nevertheless, although transient, some arrhythmias can cause syncope (tachyarrhythmias or bradyarrhythmias). A 24-hour ECG recording (Holter recording) can often uncover these intermittent events.

How are disorders characterized by dyssynergy of contraction detected on physical examination?

These may be inferred by detecting an irregular cardiac rhythm on auscultation or on femoral arterial palpation. An irregular cardiac rhythm that occurs at a fast heart rate is always due to a pathologic process. An irregular rhythm that occurs at a low normal heart rate may be normal (sinus arrhythmia). Some dysrhythmias occur with a regular cardiac rhythm, thus the absence of an irregular cardiac rhythm does not rule out the possibility of a disorder of synergy of contraction (dysrhythmia).

Pulse deficits (the absence of a peripheral arterial pulse induced by the heart beat) may be detected if the cardiac rhythm is irregular. Pulses of greatly variable intensity may also be noted.

The electrocardiogram is the best diagnostic aid to identify and verify these abnormalities. For intermittent arrhythmias, a Holter recording may be required.