Type I myocardial rupture due to atrioventricular discontinuity in the region of the posterior mitral annulus is a fearsome and nearly unpredictable complication of mitral valve replacement. We report a case of a 49-year-old patient who had been operated on for mitral valve replacement. The posterior mitral leaflet had heavy calcifications embedded through the annulus in the posterior ventricular wall. After removal of calcifications we avoided the risk of myocardial rupture by suturing a straddling pericardial patch on the atrioventricular junction. The operation resulted in complete recovery.