7th March 2024

Signs and symptoms

The commonest presenting symptom in HCM is dyspnea, but it can also present with chest pain, palpitations and syncope.

Systolic function as measured by ejection fraction is typically preserved, though abnormalities of contractile function are often seen when assessing ventricular deformation parameters (LV global longitudinal strain and strain rate), while diastolic function is often impaired by the abnormalities of the hypertrophied musculature and failure of myocardial relaxation. Dyspnea thus occurs due to elevated intracardiac pressures as the myocardium fails to relax adequately to maintain low intrachamber pressures leading to raised pulmonary artery pressures.

Chest pain can occur due to the increased metabolic demands of the hypertrophied muscle. If the hypertrophy outstrips the vascular supply, then a supply/demand mismatch can lead to relative ischaemia despite normal epicardial coronary vessels.

Palpitations can occur due to arrhythmias generated in the hypertrophied muscle. Ventricular arrhythmias are not uncommon and are a cause for concern, with intervention with antiarrhythmics or device therapy commonly considered.

LVOT obstruction can occur due to hypertrophy of the septal myocardium. This interferes with the normal flow of blood through the LVOT and, ultimately, the aortic valve. If this is sufficiently diminished, then blood will not reach the aorta to perfuse the coronary arteries nor the carotid arteries to perfuse the brain. This can lead to chest pain in the former and syncope or presyncope in the latter. These are concerning symptoms in HCM and require urgent investigation, as unexplained syncope in the context of HCM is a significant risk marker for sudden cardiac death.

Classical examination findings include a forceful, non-displaced apical beat accompanied by a jerky (otherwise called bisferiens) pulse. The irregular pulse of atrial fibrillation is a common finding, seen in approximately 1/5 of patients.

On auscultation, if the outflow tract is obstructed one can hear a systolic murmur radiating to both mitral and aortic regions, with the volume increased on Valsalva and diminished on release. This occurs because in Valsalva there is less venous return due to the increased intrathoracic pressure. This leads to an underfilled left ventricle, allowing the septum to block off the outflow tract. Conversely, when Valsalva is released, increased blood flow helps to splint open the outflow tract, reducing the obstruction and thus reducing the murmur. An additional sound of an S4 can also be heard due to turbulent flow in a non-compliant ventricle.

In comparison, the opposite effect is seen in aortic stenosis, in which a reduction in flow due to Valsalva leads to a quieter murmur, while the increase in flow post Valsalva causes a louder murmur due to more turbulent flow through the stenotic valve.