What can cause reflex tachycardia?

If blood pressure decreases, the heart beats faster in an attempt to raise it. This is called reflex tachycardia. This can happen in response to a decrease in blood volume (through dehydration or bleeding), or an unexpected change in blood flow.

How does prazosin cause reflex tachycardia?

Postural hypotension and reflex tachycardia, particularly on standing, are features of the first-dose response to prazosin, but adaptive receptor responses lead to re-setting of the reflex mechanisms within the first few days of treatment, and there are therefore generally no significant changes in heart rate during …

Why does hydralazine cause reflex tachycardia?

Hydralazine, which is highly specific for arterial vessels, reduces systemic vascular resistance and arterial pressure. Indirect cardiac stimulation (e.g., tachycardia) occurs with hydralazine administration because of activation of the baroreceptor reflex.

Why does phentolamine cause tachycardia?

In contrast, the blood pressure lowering effects of non-selective alpha blockers, such as phentolamine, are associated with a marked reflex tachycardia due to blunting of inhibitory presynaptic α2 feedback that suppresses the release of norepinephrine when synaptic levels of the neurotransmitter rise.

Why does vasodilators cause reflex tachycardia?

While vasodilators are successful in controlling hypertension, these medications possess a myriad of side effects. Reflex tachycardia is the primary adverse effect of these drugs, as a consequence of the medication induced baroreflex response compensating for the sudden medication decrease in vascular resistance.

What receptors does prazosin work?

Prazosin acts primarily by blocking α1-adrenergic receptors but also peripherally inhibits phosphodiesterase. Since prazosin does not block α2-adrenergic receptors, noradrenaline (norepinephrine) release is still controlled via negative feedback.

Where are alpha 1 receptors located?

vascular smooth muscle
Alpha 1 receptors are the classic postsynaptic alpha receptors and are found on vascular smooth muscle. They determine both arteriolar resistance and venous capacitance, and thus BP.

Do alpha 1 antagonists cause reflex tachycardia?

Reflex tachycardia is weak or absent, owing to the following mechanisms: (1) The absence of presynaptic alpha 2-receptor blockade, thus preventing the accelerated release of noradrenaline from the nerve endings; and (2) the blockade of central alpha 1-adrenoceptors, causing a blunting of the reflex tachycardia via the …

Why ACE inhibitors do not cause reflex tachycardia?

The fall in blood pressure following ACE inhibition is not associated with changes in heart rate; in particular, there is no reflex tachycardia. ACE inhibitors vary in efficacy and duration of action with some but not others being suitable for once-daily dosing.

Why does nifedipine cause reflex tachycardia?

Nifedipine is a dihydropyridine calcium channel blocker, the short acting formulation of which has been associated with reflex sympathetic nervous system (SNS) activation leading to flushing, tachycardia, worsening myocardial ischemia, and cerebrovascular ischemia; therefore only longer acting formulations should be …

Do beta-blockers cause reflex tachycardia?

Beta-blocker withdrawal. Abrupt discontinuation of beta-blockers can lead to a “rebound” effect characterized by tachycardia and hypertension. Patients with ischemic heart disease may have exacerbation of angina or acute ischemic events.

What happens when alpha-1 receptors are blocked?

Alpha-1 blocker lowers the blood pressure by blocking alpha-1 receptors so norepinephrine cannot bind the receptor, causing the blood vessels to dilate. Without the resistance in the blood vessels the blood runs more freely.

Where are alpha-1 receptors located?

Which CCB causes reflex tachycardia?

Dihydropyridine CCBs can cause flushing, headache, excessive hypotension, edema and reflex tachycardia.