Abnormalities of heart rate and rhythm can occur due to action of several mast cell mediators. Histamine binds at histamine receptors numbered in the order of identification: H1, H2, H3 and H4. Histamine binding at H1 receptors on cardiomyocytes (heart muscle cells) slows the heart rate, while histamine binding at H2 receptors increasing heart rate and the force of heart contraction.
As I mentioned in the previous post, histamine binding at the H3 receptor decreases the release of norepinephrine. Another mast cell product, renin, modulates angiotensin II, which can increase norepinephrine release. Increased levels of norepinephrine triggers increases in heart rate and force of contraction. This means that whether or not mast cell activation causes tachycardia depends largely on how much renin and histamine are released. Much less histamine is necessary to trigger the H3 inhibition of norepinephrine release relative to the amount needed to affect heart rate through H1 and H2 receptors.
Prostaglandin D2, a mast cell mediator, can also cause tachycardia. Of note, prostaglandin D2 is not stored in mast cell granules. It is made following mast cell activation and is considered part of the “late phase allergy response”, which can occur several hours after exposure to a trigger.
Tachycardia is a common symptom for mast cell patients. The recommendation in a recent review article is to treat when the heart rate is perpetually over 100-120 bpm, or when it is extremely distressing to the patient. There are a number of options for treatment. As it can be caused directly by mast cell behavior, mast cell medications such as antihistamines (H1 and H2) should be adjusted for maximum effect. Renin inhibitors, such as aliskiren (Tekturna in the US), can be used to treat supraventricular tachycardia (SVT) in mast cell patients, as can angiotensin receptor blockers like losartan, valsartan and others. Patients on renin inhibitors or angiotensin receptor blockers can also decrease blood pressure.
Calcium channel blockers, like verapamil, are also an option. The medication ivabradine treats tachycardia in patients who have a regular heart rhythm and does not affect blood pressure. Ivabradine is not used to treat atrial fibrillation. β-blockers are contraindicated in mast cell patients because it interferes with the action of epinephrine, making patients more likely to have reactions and epinephrine less likely to treat effectively.
Kolck UW, et al. Cardiovascular symptoms in patients with systemic mast cell activation disease. Translation Research 2016; x:1-10.
Gonzalez-de-Olano D, et al. Mast cell-related disorders presenting with Kounis Syndrome. International Journal of Cardiology 2012: 161(1): 56-58.
Kennedy S, et al. Mast cells and vascular diseases. Pharmacology & Therapeutics 2013; 138: 53-65.