Late systolic murmurs and non-ejection ("mid-late") systolic clicks. An analysis of 90 patients.

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Abstract
Studies were made of 90 patients with either a late systolic murmur (15), a non-ejection systolic click (37), or both (38). Cine-angiocardiography, the responses of the auscultatory signs to vasoactive maneuvers, intracardiac phonocardiography, and anatomical evidence confirm that late systolic murmurs denote mild mitral incompetence and suggest that non-ejection clicks result from functionally unequal length of chordae tendineae. From the fairly constant pattern of response of late systolic murmurs and non-ejection clicks to hemodynamic alterations (erect posture, amyl nitrite, phenylephrine, the Valsalva maneuvre anxiety and isoprenaline , the factors that affect the functional anatomy of the mitralvatve mechanism, and hence the intensity and timing of the murmurs and click, can be determined. An abnormally billowing mitral posterior leaflet is often demonstrated cine-angio-cardiographically in patients with late systolic murmurs. A voluminous posterior leaflet was observed at necropsy in 1 case. A not infrequent association of this posterior leaflet anomaly with an abnormal ecg pattern, the appearances of which suggest postero-inferior myocardial ischemia, constitutes a specific ausculatory ecg syndrome. The prognosis of this syndrome is uncertain and sudden death may occur. The cause and explanation of the ecg changes still require elucidation. Diverse etiological factors affecting the mitralvatve mechanism can result in a late systolic murmur or non-ejection click. These include direct or indirect trauma, rheumatic endocarditis, Mar-fan''s syndrome, hypertrophic obstructive cardiomyopathy, myocardial or papillary muscle ischemia, and mitral valve surgery. Although in many instances no etiological factor is incriminated, in some of these an hereditary factor exists. Irrespective of the etiology, functional inequality of chordae and an abnormal degree of leaflet billowing may occur at all patients with late systolic murmurs of non-ejection clicks. The possibility that these changes may progress to cause more severe mitral regurgitation is briefly discussed. An unusual form of non-ejection systolic click, occurring early in systole but varying spontaneously in timing, developed after mitral valvotomy in 6 patients. Such post-vatvotomy clicks are seldom recognized, and must be distinguished from components of the 1st sound and ejection clicks.