Antiarrhythmics - Class IV (Ca2+ channel blockers) 2

Question 1

Calcium is released into the smooth muscle of the blood vessels and cardio myocytes which contribute to vasoconstriction. What is the mechanism of action of Ca+ channel blockers?

1 - binds and inhibits angiotensin II receptors
2 - inhibits ACE
3 - inhibit beta receptors
4 - binds and inhibits L-type Ca2+ channels

Answer 1

4 - binds and inhibits L-type Ca2+ channels

• non competitive antagonist
• ⬇️ Ca2+ in vascular and cardiac cells and inhibit vasoconstriction so good for blood pressure
• reduces Ca2+ released into myocytes lowering force of contraction

Question 2

Which of the following are calcium channel blocker medications that we need to know from our core drug list?

1 - Ramipril, Diltiazem, Verapamil
2 - Amlodipine, Ramipril, Verapamil
3 - Amlodipine, Bisoprolol, Verapamil
4 - Amlodipine, Diltiazem, Verapamil

Answer 2

4 - Amlodipine, Diltiazem, Verapamil

• remember DAV

Question 3

Which of the following drugs is the first line drug for hypertension, using the cuts offs below in a patient aged >55 y/o and black ethnicity?

• Stage 3: SBP >180 mmHg Treat immediately
• Stage 2: BP >160/100 mmHg Treat once confirmed on 24hr BP
• Stage 1: BP > 140/90 mmHg Treat if end-organ damage or if diabetic

1 - ace inhibitors (ACE-I)
2 - calcium channel blockers
3 - alpha blockers
4 - angiotensin receptor2 blockers

Answer 3

2 - calcium channel blockers

• Amlodipine would be the first choice for hypertension
• Verapamil is 1st choice for arrhythmias
• Diltiazem is bit of cardiac and vascular
• remember DAV
• essentially when an ACE-I or ARB-II are unsuitable

Question 4

Calcium channel blockers (CCB) are indicated in patients with ischaemic heart disease. There are 2 types of CCB:

• dihydropyridines
• nondihydropyridines

Which of these acts predominantly on vascular cells and which acts predominantly on cardiac cells?

Answer 4

• dihydropyridines =
  vascular cells
• nondihydropyridines = cardiac cells

Question 5

There are 3 key calcium channel blockers that we need to be aware of: Amlodipine, Diltiazem, Verapamil. Which of these 3 drugs is a dihydropyridines, and preferrentially targets the vasculature cells?

1 - Amlodipine
2 - Diltiazem and Verapamil
3 - Amlodipine and Diltiazem
4 - all 3 drugs

Answer 5

1 - Amlodipine

Question 6

There are 3 key calcium channel blockers that we need to be aware of: Amlodipine, Diltiazem, Verapamil. Which of these 3 drugs is a non-dihydropyridines, and preferentially targets the cardiac cells?

1 - Amlodipine
2 - Diltiazem and Verapamil
3 - Amlodipine and Diltiazem
4 - all 3 drugs

Answer 6

2 - Diltiazem and Verapamil

• varapamil is the most cardioselective

Question 7

There are 3 key calcium channel blockers that we need to be aware of: Amlodipine, Diltiazem, Verapamil. Which of these 3 drugs is indicated in controlling heart rate in patients with supraventricular arrhythmias, including atrial fibrillation, atrial flutter and supraventricular tachycardia?

1 - Amlodipine
2 - Diltiazem and Verapamil
3 - Amlodipine and Diltiazem
4 - all 3 drugs

Answer 7

2 - Diltiazem and Verapamil

• non-dihydropyridines which are the most cardiac cell specific
• varapamil is the most cardioselective

Question 8

Verapamil and Diltiazem are the two most cardiac selective calcium channel blockers. Which of the following is NOT an affect they have on the heart?

1 - suppress cardiac conduction, particularly across the AV node
2 - reduce ventricular rate
3 - increase contractility
4 - reduce afterload and therefore myocardial oxygen demand

Answer 8

3 - increase contractility

• they actually reduce contractility

Question 9

There are 3 key calcium channel blockers that we need to be aware of: Amlodipine, Diltiazem, Verapamil. Verapamil is a non-dihydropyridines, and preferentially targets the cardiac cells. Which of the following is NOT a common adverse effect of Verapamil?

1 - constipation
2 - heart block
3 - cardiac failure
4 - ankle swelling
5 - bradycardia

Answer 9

4 - ankle swelling
- not common with verapamil

• Diltiazem can affect cardiac and vascular cells, so can cause these effects

Question 10

Verapamil and diltazem should be used with caution in patients with impaired left ventricular function. Why is this?

1 - precipitate or worsen heart failure
2 - vasodilatory affects increase pressure on heart
3 - increase SVR and therefore the pressure on the heart
4 - damage the aortic valve

Answer 10

1 - precipitate or worsen heart failure

Question 11

Verapamil and diltazem should be avoided in patients with AV nodal block. Why is this?

1 - can cause flushing
2 - can cause headaches and increase heart rate
3 - can cause heart block
4 - increase SVR and therefore the pressure on the heart

Answer 11

3 - can cause heart block

• if AV node conduction is slow already, Verapamil and diltazem could make it worse

Question 12

There are 3 key calcium channel blockers that we need to be aware of: Amlodipine, Diltiazem, Verapamil. Verapamil and Diltiazem are non-dihydropyridines, and preferentially targets the cardiac cells. These drugs should not be used in conjunction with which other class of anti-hypertensives?

1 - ACE inhibitors
2 - Angiotensin-II receptor blockers
3 - α-blockers
4 - β-blockers

Answer 12

4 - β-blockers

• non-dihydropyridines and B-blockers are negatively inotropic and chronotropic
• inotropic affects contractility of the heart
• chronotropic affects the rate of the heart
• together both could cause heart failure, bradycardia or asytole and should only be used under close supervision

Question 13

What is the standard dose patients are prescribed verapamil for supreventrivcular tachycardia?

1 - 4-20mg 8/h
2 - 30-50mg 8/h
3 - 50-90mg 8/h
4 - 40-120mg 8/h

Answer 13

4 - 40-120mg 8/h