MPS I: Associated Cardiac Complications

For children with severe MPS I, death in the first 10 years of life is often due to cardio-respiratory complications. For those with moderate MPS I, cardiac involvement is usually milder and survival into adulthood is common.

Cardiac Problems

  • Thickening of the mitral and aortic valves, leading to regurgitation or stenosis
  • Myocardial thickening that contributes to heart failure
  • Cardiac arrhythmias leading to heart block, resulting in the need for a permanent pacemaker
  • Narrowing of the coronary arteries, often within the first year of life - complete occlusions of the coronary arteries have been reported within the first 5 years of life, with sudden death occurring during illness or with blood pressure changes associated with anesthesia.
  • Narrowing of the thoracic aorta, possibly resulting in elevated blood pressure in the head and neck with normal blood pressure in the legs
  • Congenital cardiac abnormalities, including ASD or PDA, may occasionally be present in children who have MPS Syndromes.
  • Cor Pulmonale is a rare complication of MPS I.


  • Cardiology consultation is strongly recommended - absence of a murmur on physical exam does not exclude cardiac involvement.
  • Tachycardia may be present due to aberrant conduction pathways (usually treatable by conventional means).
  • Coronary artery involvement is difficult to assess because of the diffuse involvement (as opposed to the focal narrowing more commonly encountered). It is best to assume coronary involvement if there is evidence of substantial deposition of glycosaminoglycan in other parts of the heart, such as the valves or walls.


  • Regular follow-up (1-2 years) by cardiac ultrasound, electrocardiogram, and Holter monitoring by a cardiologist familiar with the complications of MPS is important.
  • Virtually all MPS I patients require SBE prophylaxis at the time of dental or other contaminated procedures. Some long-term beneficial effects of bone marrow transplantation on the heart have been documented. [Braunlin: 2003]
  • The cardiac effects of enzyme replacement therapy have yet to be described in any MPS Syndrome.



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Author: Pilar L. Magoulas, MS, CGC - 2/2009
Content Last Updated: 11/2011

Page Bibliography

Braunlin EA, Stauffer NR, Peters CH, Bass JL, Berry JM, Hopwood JJ, Krivit W.
Usefulness of bone marrow transplantation in the Hurler syndrome.
Am J Cardiol. 2003;92(7):882-6. PubMed abstract
Patients studied 10 years post BMT did not display signs of congestive heart failure or die from coronary artery occlusion. Cardiac function remained normal in all patients with the size of the left ventricular chamber at near-normal values. However, valvular involvement was not altered, continuing to thicken and develop prolapse, insufficiency or stenosis. The aortic valve, rather than the mitral valve, seemed most affected in patients who had undergone BMT compared to untreated patients.