Implications of cardiac drugs Flashcards
What are ACE i used for
HPT. Compelling indication in diabetes to prevent diabetic nephropathy
Symptomatic LV dysfunction (afterload reduction)
What are the side effects of ACEi
- Cough (bradykinin)
- Angioedema
- Concomitant use with NSAID increase risk of renal damage
- Hypotension with GA
List the clinical indications for beta blockers
HPT HF Arrhythmia Angina Other (anxiety)
How do BB lower BP
Decrease CO - Negative inotropy and chronotropy
Alter baroreceptor sensitivity
Reduce renin secretion
Why are BB used for angina
Beta-blockers improve exercise tolerance and relieve angina symptoms by reducing the heart rate.
Why are BB prescribed after MI
Beta-blockers reduce the recurrence rate after MI.
List the ‘other’ uses for BB
Heart failure Thyrotoxicosis Anxiety Migraine prophylaxis Glaucoma (topical)
What are the side effects of BB
Bradycardia
Heart block
Heart failure
Mask autonomic response to hypoglycaemia
When are BB contraindicated
2nd/3rd degree heart block
Unstable heart failure
Asthma
Name 3 clinical indications for nitrates (GTN or isosorbide mononitrate
- Prophylaxis and treatment of angina
- Relief of cardiac ischaemic pain
- Prophylaxis and treatment of LVF
What are the side effects of Nitrates
Headache
Postural hypotension
Flushing
List the clinical indications for CCB
HPT
Prophylaxis of angina
SVT
What are the side effects of CCB
Hypotension
Bradycardia
Pedal oedema
What are the side effects of diuretics
Hypokalaemia
Hyponatraemia
Hypomagnasaemia
Postural hypotension
List the clinical indications for nicorandil and state its MOA
Prevention and long-term treatment of angina
MOA: K+ channel activator –> vasodilation
List the side effects of K+ channel activators
Bradycardia
First degree heart block
Ventricular extrasystoles
A patient with a drug-eluting cardiac stent is likely to be taking clopidogrel: true or false and why
True. The British Cardiovascular Interventional Society advise that patients with drug-eluting cardiac stents usually require clopidogrel for at least 12 months following their percutaneous coronary intervention. In these patients, clopidogrel should not be stopped without discussion with a cardiologist.
True or false and why: Digoxin, amiodarone and mexiletine may all be used for the treatment of supraventricular tachyarrythmias (SVT)
False. Digoxin and amiodarone are used for SVTs. However,
True or false and why: Impaired renal function may result from treatment of high cholesterol with a statin
False. Liver impairment may result, not renal impairment.
Why is clopidogrel important perioperatively
- Neuraxial blocks are contraindicated within 5 - 7 days of stopping clopidogrel due to risk of bleeding
- There is risk of stent thrombosis if clopidogrel is stopped during critical periods following insertion
- There is risk of excessive bleeding during surgery
What are the clinical indications for statins
Reduced LDL
Reduce CVS events: coronary, cerebral, peripheral
Reduce total mortality from CVS evetns
What are the side effects of statins
Impairment of liver function and deranged LFTs
Muscle pains
Rhabdomyolysis
What are the clinical indications for digoxin
Rx SVT (with impaired EF)
AF
Heart failure
What are the clinical indications of amiodarone
Rx arrhythmias (SVT/VT/AF/Flutter/Tachycardia associated with WPW syndrome)
What are the clinical indications for alpha blockers
Prostatic hyperplasia Resistant HPT (along with BB)
What are the side effects of alpha blockers
Postural hypotension
Severe hypotension with anaesthesia (Hold > 24hrs preop)
Which CVS drugs are considered UNSAFE TO STOP in the perioperative period
Beta blockers (rebound ACS/arrhythmias)
Statins (stabilize atheromatous plaques - omission may result in rupture)
Anticoagulants
- clopidogrel: consult cardiology (usually must be continued)
- Warfarin changed to LMWH/UFH
- Aspirin: continue
Which drugs should be omitted on the day of surgery
- ACEi (profound hypotension during anaesthesia)
2. alpha antagonists (Stop if used for BPH)
How do thiazide diuretics cause hypokalaemia
Thiazides inhibit sodium reabsorption in the early DCT. The delivery of Na to the distal Na/K exchange site is increased –> increased Na/K exchange and increased K excretion
How do loop diuretics cause hypokalaemia
Inhibit Na-K-Cl transporter in TAL LOH –> Increase Na delivery to distal nephron leading to increased K secretion and excretion
How do ACEi and ARBs cause hypokalaemia
By inhibition of aldosterone release
Which electrolyte abnormalities precipitate digoxin toxicity
Hypokalaemia
Hypomagnasaemia
Hypercalcaemia
What are the ECG findings in digoxin toxicity
Prolonged PR
Heart block
T - wave inversion
ST depression (reverse tick)
When should surgery be cancelled in the context of hypokalaemia
K < 3.5 if the patient taking digoxin and/or other anti-arrhythmic or in the presence of severe cardiac disease
In fit patients not on anti-arrhythmics a potassium of 2.5 to 3.5 may be acceptable
What Urea : Creatinine ratio suggests a pre-renal cause
2:1
List the the haematological parameters and factors in which neuraxial blockade should be avoided
INR > 1.4 APTR > 1.4 Plts < 80 x 10^9/L Clopidogrel < 7 days UFH < 4 hours Prophylactic dose LMWH < 12 hours Treatment dose LMWH < 24 hours
How long does IV vitamin K take to normalize INR
24 hours
What can be administered for more rapid correction of INR
PCC
FFP
How are ultrasound waves generated
When a voltage is applied to a piezoelectric crystal the crystals distort creating mechanical and kinetic energy
How are ultrasound waves measured/received
Sound waves returning to the piezoelectric crystal cause mechanical distortion of the crystal which generates a voltage. The time taken for this voltage to be generated is measured and the distance away from the probe that these reflected sound waves originate can be calculated and an image formed on the monitor.
What is the doppler principle
Due to the movement of the red blood cells the transducer detects a change in frequency of the ultrasound waves
Velocity = frequency (cycles/s) x wavelength (m).
As the blood cell moves towards the transducer the wavelength appears shorter because the high pressure regions of the wave become closer together –> this shortening of the wavelength is picked up as an increased frequency and it is the change in frequency which is used to calculate the velocity of the blood cells
What are the three different types of Doppler Echocardiography
Continuous waveform Doppler
Pulsed wave Doppler
Colour Doppler
What is the frequency range for ultrasound waves?
2.5 to 5 kHz
What is continuous wave Doppler used for
To measure the peak velocity across the valve and to calculate the gradient across the valve and give and indication of severity of the lesion
What are the indications for ECHO for the assessment of LV function
Symptoms and signs of heart failure
Unexplained dyspnoea where no respiratory cause has been found for their symptoms
IHD and poor exercise tolerance for patients who have never had an echo or have had a deterioration in symptoms since their last echo
Known ventricular impairment for patients who have had a deterioration in symptoms since their last echo
What are the indications for ECHO for the assessment of valve function
- Undiagnosed murmur
2. Valve disease with worsening symptoms
What is normal EF
> 60%
What is severely impaired EF
< 40%
What is the normal valve area of the aortic valve
2.6 - 3.5 cm^2
What is the normal area of the mitral valve
4 - 6 cm^2
What are the advantages and limitations of TTE
Advantage: Easy to obtain and noninvasive
May get poor views in patients with obesity, lung disease and chest wall deformity
What are the advantages and limitations of TOE
Advantage
- better for looking at posterior structures (left atrium and descending aorta)
- Used to look for endocarditis and aortic dissection
- Useful in patients that are poor subjects for TTE
Disadvantage - Invasive
What is a stress ECHO
Dobutamine used to simulate ‘exercise’
Wall motion abnormalities that develop after the dobutamine is started indicate areas of myocardial ischaemia, whereas those present at the start indicate areas of infarction.
Is an ECHO required if ventricular function was assessed during angiography?
No.
What type of CT can be used to image the heart?
Electron beam CT is high speed and provides good resolution as it minimizes cardiac and respiratory motion interference
What is myocardial perfusion scintigraphy
Radioactive tracer (Thallium 201) Areas of ischaemia show up as defects as the radioactive tracer requires coronary blood flow to be delivered to the myocardium Defects present at rest are due to infarct. Defects present after stress are due to ischaemia
Describe the Bruce protocol used in treadmill testing
7 stages of 3 minutes each
- Stage 1: 2.7 kmph at 10% incline = 4.8 METs
(each subsequent stage the speed is increased by 1.12 kmph and 2% incline)
What is a modified Bruce protocol
Used for exercise testing within 1 week of MI - starts at lower work level and so takes longer to achieve the required heart rate
