Session 6 - Group Work Flashcards
1a) List the phases of the cardiac action potential and the principle ion fluxes at each stage
Phase 0 - Na+ influx Phase 1 - K+ efflux Phase 2 - Ca2+ influx Phase 3 - K+ efflux Phase 4 - Na/K ATPase
1b) What are the principle difference between cardiac muscle, vascular smooth muscle and voluntary muscle regarding dependency on Ca for contraction?
You need the cardiac and vascular smooth muscle you need an initial influx of calcium to stimulate the AP
For voluntary muscle the neurotransmitter causes the release of calcium from the sarcoplasmic reticulum, so calcium is not needed for initial depolarisation directly.
1c) List the classes in the Vaughan Williams Classification of antiarrhythmic drugs.
Class I - sodium-channel blocker
IA - moderate
IB - weak
IC - strong
Class II - beta-blocker
Class III - potassium-channel blocker
Class IV - calcium-channel blocker
1d) What are the commonly used drugs in each class? [in the Vaughan Williams Classification]
Class IA - quinidine
IB - Lidocaine
IC - Flecainide
Class II - Bisoprolol
Class III - Amiodarone
Class IV - Verapamil
1e) How does digoxin act on the heart and what are its principal uses clinically?
Digoxin is a cardiac glycoside that increases the force of myocardial contraction and reduces conductivity within the atrioventricular (AV) node.
2) A 55-year old woman with known mild mitral valve disease is admitted via A&E having collapsed in Tesco while shopping. She is found to have a pulse rate of 150 beats per minute, which is irregularly irregular. Blood pressure is 120/65. She is otherwise quite comfortable. Blood tests performed are normal except for a raised serum creatinine of 150 mmol/l (normal < 120 mmol/l).
a) What is the most likely cause of her arrhythmia?
Atrial fibrillation
2) A 55-year old woman with known mild mitral valve disease is admitted via A&E having collapsed in Tesco while shopping. She is found to have a pulse rate of 150 beats per minute, which is irregularly irregular. Blood pressure is 120/65. She is otherwise quite comfortable. Blood tests performed are normal except for a raised serum creatinine of 150 mmol/l (normal < 120 mmol/l).
b) How would you confirm the diagnosis?
ECG
Blood tests
Stress test
Chest x-ray
Check GFR
2) A 55-year old woman with known mild mitral valve disease is admitted via A&E having collapsed in Tesco while shopping. She is found to have a pulse rate of 150 beats per minute, which is irregularly irregular. Blood pressure is 120/65. She is otherwise quite comfortable. Blood tests performed are normal except for a raised serum creatinine of 150 mmol/l (normal < 120 mmol/l).
c) What drug treatments would you consider, what are their mechanisms of action and how can they be administered?
You could use beta blockers - e.g. bisoprolol, and warfarin
The AF is acute, unstable and less than 48 hour duration. We can cardiovert her electrically (e.g. defibrillate).
Adenosine could be used to cardiovert.
Digoxin can be used for patients with heart failure to reduce load on the heart
2) A 55-year old woman with known mild mitral valve disease is admitted via A&E having collapsed in Tesco while shopping. She is found to have a pulse rate of 150 beats per minute, which is irregularly irregular. Blood pressure is 120/65. She is otherwise quite comfortable. Blood tests performed are normal except for a raised serum creatinine of 150 mmol/l (normal < 120 mmol/l).
d) What are the potential hazards of the use of digoxin in this patient and what precautions would you take?
The patient has reduced kidney function, so the use of digoxin needs to be monitored as it won’t be cleared as efficiently as a patient who does not have impaired renal function.
3) A 74 year old female with a history of atrial fibrillation has successfully had surgery to for a Carbomedics aortic valve replacement (low thrombogenicty risk). She requires anticoagulation therapy following the surgery.
Her baseline INR is 1.1.
a) What is the target INR for this patient?
3.5 +/- 0.5
3) A 74 year old female with a history of atrial fibrillation has successfully had surgery to for a Carbomedics aortic valve replacement (low thrombogenicty risk). She requires anticoagulation therapy following the surgery.
Her baseline INR is 1.1.
The attending doctor prescribes an initial dose of warfarin on day 1.
b) Her INR on day 2 is 1.1. What dose of warfarin should be prescribed?
5.0 mg
3) A 74 year old female with a history of atrial fibrillation has successfully had surgery to for a Carbomedics aortic valve replacement (low thrombogenicty risk). She requires anticoagulation therapy following the surgery.
Her baseline INR is 1.1.
The attending doctor prescribes an initial dose of warfarin on day 1.
c) Her INR on day 3 is 3.4. What dose of warfarin should be prescribed?
1.0 mg
3) A 74 year old female with a history of atrial fibrillation has successfully had surgery to for a Carbomedics aortic valve replacement (low thrombogenicty risk). She requires anticoagulation therapy following the surgery.
Her baseline INR is 1.1.
The attending doctor prescribes an initial dose of warfarin on day 1.
d) Could a NOAC be prescribed instead?
No, because patients on NOACs had too many thromboembolic events
Every patient with a prosthetic heart valve needs to be on warfarin for anticoagulation. However, a study shows that NOACs shouldn’t be given to this group of patients i.e. they can be used for other patients with heart problems but not in mechanical heart valves.
3) A 74 year old female with a history of atrial fibrillation has successfully had surgery to for a Carbomedics aortic valve replacement (low thrombogenicty risk). She requires anticoagulation therapy following the surgery.
Her baseline INR is 1.1.
The attending doctor prescribes an initial dose of warfarin on day 1.
e) The following day the INR was 0.5 below the target level. What course of action should be taken?
Change the dose following guidelines to 3.5 mg
4) A 58 year old man presents in the emergency department with central crushing chest pain and breathlessness. It is ascertained that he has been experiencing this pain for nearly two hours. He is hypertensive and has recently being diagnosed with type II diabetes. He had a 20 pack years smoking habit which he reduced to 0.1 pack years last year.
Pulse 80, BP 143/78, Sats 96%, RR 16 Blood results include INR 1.2
The most recent ECG upon arrival shows sinus rhythm and 3mm depression leads II, III and AVF. By this stage the pain is subsiding.
a) With the information provided what diagnoses would you make?
NSTEMI
Unstable angina (troponin to differentiate)
