Can Polycythemia Vera Cause Heart Murmurs?
Yes, polycythemia vera can cause heart murmurs, primarily through hyperviscosity-related increased cardiac output and flow-related phenomena, though this is not a direct or commonly emphasized manifestation of the disease.
Mechanism of Murmur Generation in Polycythemia Vera
The pathophysiologic basis for murmurs in PV relates to altered blood rheology and compensatory hemodynamics:
Increased blood viscosity from elevated hematocrit (the major determinant of whole blood viscosity, especially at low shear rates) creates abnormal flow dynamics that can generate flow murmurs 1
Hyperviscosity states with elevated cardiac output can produce midsystolic (systolic ejection) murmurs similar to those seen in other high-flow states like anemia, thyrotoxicosis, and pregnancy 1
The ACC/AHA guidelines explicitly recognize that midsystolic murmurs may be caused by increased flow rate occurring with elevated cardiac output, and PV creates a paradoxical situation where despite increased red cell mass, the heart must work harder to maintain tissue perfusion through hyperviscous blood 1
Clinical Context and Pre-existing Heart Disease
In patients with pre-existing cardiac conditions, PV significantly amplifies cardiovascular risk:
Thrombotic complications are the major cause of morbidity and mortality in PV, with cardiovascular death and major thrombosis occurring in 9.8% of inadequately controlled patients versus 2.7% in those maintained at hematocrit <45% 2
Microvascular circulatory disturbances including peripheral ischemia and atypical cerebral ischemic attacks are positively related to hematocrit levels due to increased whole blood viscosity 3
Myocardial microinfarcts from abnormal blood flow in small coronary vessels can occur in PV, potentially leading to dilated cardiomyopathy and heart failure with associated murmurs from ventricular dysfunction or functional valvular regurgitation 4
Patients with PV can develop functional mitral or tricuspid regurgitation secondary to ventricular dilatation from chronic volume overload or ischemic cardiomyopathy, which would produce holosystolic murmurs 1
Important Clinical Caveats
The murmur itself is not a diagnostic feature of PV - the disease is primarily identified through elevated hemoglobin/hematocrit (>16.5 g/dL/49% in men, >16 g/dL/48% in women), JAK2 mutation, and bone marrow findings 5. The classic clinical phenotype includes plethora (ruddy discoloration), engorged veins, and conjunctival injection rather than cardiac auscultatory findings 6.
Do not attribute a new murmur solely to PV without excluding structural cardiac disease, particularly given that:
- PV patients have substantially elevated thrombotic risk requiring aggressive hematocrit control 2
- Coronary and valvular pathology may coexist and require specific intervention 4
- Echocardiography is necessary to distinguish flow murmurs from structural valve disease 1
Management Implications
Maintain hematocrit <45% through phlebotomy as the cornerstone of treatment, which reduces cardiovascular death and major thrombosis risk by approximately 70% 2
Phlebotomy reduces whole blood viscosity and can eliminate or diminish flow-related murmurs, though it does not necessarily improve tissue oxygenation 1
In patients with documented cardiac disease and PV, careful fluid management during phlebotomy is essential to avoid hypotension or fluid overload 1
Aspirin therapy (81 mg once or twice daily) is indicated for all PV patients without contraindications to prevent thrombotic complications 5