Neurocardiogenic syncope, also called vaso-vagal syncope or “simple faints” is the most common type of syncope, not usually causally associated with hypertension.
Beta receptors are of 2 types: Beta-1 and Beta-2. Those in the heart are mostly Beta-1; those in the lungs, mostly Beta-2. Beta-blockers come in 2 forms: selective and non-selective. Selective beta-blockers, such as metoprolol, act primarily on the Beta-1 receptors in the heart. Non-selective beta-blockers, such as propranolol act on both types of receptors, in both heart and lungs. Propranolol and other medicines in its class are capable of evoking bronchospasm in people with asthma. Metoprolol is selective, but not entirely so; thus, asthma worsens in some people given this “selective” medicine and you may be one of them.
Your doctor may have prescribed the metoprolol for both relief of the syncope and treatment of your hypertension. There are many other anti-hypertensive medicines that will control your hypertension without aggravating your asthma. However, if the metoprolol is absolutely necessary for the control of your syncope and there is no other medicine that will suffice you and your doctor may want to look to ways to reduce its adverse effects on your lungs. Two such would be: 1) a reduction in metoprolol dose, and 2) the addition of non cardio-stimulatory asthma medicines to your regimen to counter-act the seeming impact of the metoprolol on your lungs. This would best be expedited by a conversation between your electrophysiologist and your asthma doctor. The 2 of them could also decide upon which anti-hypertensive medicines might be best, for example hydrochlorothiazide being an effective anti-hypertensive with no effect on one’s lungs.