Saw-tooth Cardiomyopathy is a very rare disease, that should not be confused with left ventricular non compaction, and only few cases have been described.

We describe the case of a 33-year-old man who presented with atypical chest pain. The ECG showed left posterior fascicular block. Left ventricular non-compaction (LVNC) was initially suspected by echocardiography. Cardiac MRI found no criteria for LVNC but typical protrusions of muscular bridges in the left ventricle with dense compacted myocardium leading to the diagnosis of Saw-Tooth Cardiomyopathy. No arrhythmic event nor heart failure were noticed. In the family there was no cardiac history nor sudden death. We performed genetic analysis by sequencing a large panel of 71 genes associated with cardiomyopathies [Roche Nimblegen capture probes, sequencing on Miseq (Illumina)]. No pathogenic variant was found according to ACMG criteria (Fig. 1).

Less than ten cases of Saw-Tooth Cardiomyopathy (ST-CMP) were previously reported in literature and ST-CMP was initially reported as a variant of LVNC. In fact, myocardial features of ST-CMP are very different from LVNC and ST-CMP should be considered as a separate entity. Some cases were discovered during infancy suggesting prenatal development. Our case first illustrates this distinct entity since none of LVNC criteria were met but typical Saw-tooth muscular bridges that were better exhibited on MRI. Second, our case is the first to report on genetic testing and familial investigations. We did not observed other cardiomyopathy in the family and we did not identify any pathogenic mutation in known cardiomyopathy genes. Although we cannot exclude a non-genetic cause, this result may suggest a genetic cause outside the genes usually related to cardiomyopathies and suggest the search for a new gene through exome or genome sequencing.