Rigid spine syndrome: a noninvasive cardiac evaluation.

Rigid spine syndrome (RSS) is a group of childhood-onset muscle disorders characterized by marked limitation of flexion of the spine. Various cardiac changes have been documented in case reports. This study reports on a cardiac evaluation of nine patients with the "vacuolar variant" of RSS. Noninvasive cardiac evaluation entailed creatine kinase levels, full-inspiration chest roentgenograms, standard 12-lead ECG, and 24-h ambulatory ECG recording, as well as M-mode and two-dimensional echocardiography with Doppler study. Heart auscultation was abnormal in five patients. Creatine kinase MB fraction was normal in all patients. Chest roentgenogram showed scoliosis (five of nine), kyphosis (one of nine), severe anterior-posterior flattening of the chest cavity (two of nine), elevated hemidiaphragm (one of nine), caved-in appearance of upper lobes (two of nine), and symmetry of lung volumes (one of nine). Twelve-lead ECG abnormalities indicated right-sided heart disease (three of nine). Echocardiogram showed mitral valve prolapse (five of nine) with regurgitation (three of five) and evidence of pulmonary hypertension (three of nine). Ambulatory ECG recorded paroxysmal tachyarrhythmias in hypoxic or hypercapnic patients (three of nine). There was no correlation between any cardiac abnormalities and patient weakness. Mitral prolapse/regurgitation may have a developmental association with this congenital myopathy. Findings of cor pulmonale were due to the restrictive chest wall defect and respiratory muscle weakness. Paroxysmal tachyarrhythmias were due to hypoxia or hypercapnia. There was no evidence of a primary cardiomyopathy.