Ischaemic heart disease Flashcards
Classify the risk factors for IHD
Fixed
- Age
- Male Sex
- Positive family history
Modifiable
- Hyperlipidaemia
- Smoking
- Diabetes
- Hypertension
How do Long-acting nitrates treat IHD
reduces venous return and diastolic pressure, which in turn reduces the impedence to left ventricular emptying and relaxes coronary artery tone
List 3 non-pharmacological treatments for IHD
Percutaneous Transluminal Coronary Angioplasty (PCTA)
Coronary Stents (bare metal or drug eluting)
CABG
What are the pros and cons of RA versus GA in IHD
RA
PROS
- Reduced SNS response during intubation and extubation (as in GA)
CONS
- Excessive hypotension –> ischaemia
GA
PROS
- VA may improve myocardial O2 demand:supply
CONS
- SNS during intubation and extubation (attenuated using opioids/beta blockers
Describe the use of induction agents in IHD
Propofol and thipoental both cause a drop in BP, and although it may be difficult to distinguish between the two, propofol is likely to cause the greatest drop, especially if not given slowly.
Etomidate is least likely to cause hypotension, but its use is declining due to concerns over adrenal suppression.
Ketamine is relatively contraindicated because of the sympathomimetic effects which increase oxygen demand.
Which volatile agent has been associated with coronary steal phenomenon and what is this phenomenon
Isoflurane
VD of normal coronary vessels diverting blood away from diseased ones
Avoided in IHC
How can Desflurane be deleterious to a patient with IHD
At MAC >1.5 or with rapid increase of inspired concentration - sympathomimmetic effects
Describe the relevant influence of common muscle relaxants on a patient with IHD
Atracurium - H release with mild drop in BP
Rocuronium - Mild tachycardia
Vecuronium - nil
Sux - Muscle contraction –> transient increase in VR
Classify the causes of hypertension
Essential (90% of cases)
Secondary (10% of cases)
- Renal
- Endocrine
- Neurogenic
- Others
What are the renal causes of secondary hypertension
Renal artery stenosis
Polycystic Kidney Disease
Chronic Renal Failure
Glomerulonephritis
What are the endocrine causes of secondary hypertension
Primary hyperaldosteronism Phaeochromocytoma Cushing's Syndrome Acromegaly Hyper/hypothyroidism Exogenous hromonses (steroids/OCP)
What are the neurogenic causes of secondary hypertension
RICP
What are the other causes of secondary hypertension
White coat HPT Isolated systolic hypertension (elderly - calcified atherosclerosis) Sleep apnoea Pre-eclampsia Coarctation of the aorta Hypercalcaemia Hypercapnoea Porphyria
Describe how hypertension causes heart disease
Increased afterload –> LV hypertrophy –> Reduced LV compliance –> increased LVEDP –> increased LAP –> atrial fibrillation and mitral valve incompetence
LVH –> imbalanced O2 supply/demand –> remodelling –> systolic dysfunction –> reduced RBF –> activation RAAS –> salt and fluid retention.
How can myocardial ischaemia occur in the absence of coronary artery disease in the context of hypertension
Hypertrophied myocardium and afterload –> increased demand
High intramural pressure –> compromised blood and O2 supply
Should a patient with uncontrolled stage 1/2 HPT be cancelled?
It is generally agreed that patients presenting with BP <180/110 mmHg (stages 1 and 2) are not at increased risk of perioperative cardiac complications. Therefore, surgery can proceed.
However, it is important that the patient’s blood pressure is monitored very closely intraoperatively and that it is maintained within 20% of their baseline readings.
Should a patient with uncontrolled stage 3 HPT be cancelled?
For patients who present with stage 3 hypertension (BP >180/110 mmHg), the possible benefits in delaying surgery in order to control the hypertension must be considered in relation to the risks of doing so.
Even in severe hypertension, there is little evidence for delaying surgery. However, this is an area of controversy and it warrants discussion with a consultant anaesthetist.
Which antihypertensive drugs are often omitted preoperatively
ACEi
ARBs
Alpha blockers
Describe ECG evidence of LVH
There are several simple formulae to diagnose LVH on ECGs. However, sensitivity tends to be quite low.
The Sokolow and Lyon criteria:
S in V1 + R in V5 or V6 (whichever is larger) ≥35 mm
R in aVL ≥11 mm
What LVH with strain pattern
S in V1 + R in V5 or V6 (whichever is larger) ≥35 mm
R in aVL ≥11 mm
WITH inverted T waves in V4 - V6
How is a diagnosis of LVH made on ECHO
Normal LV myocardial wall thickness at the END of DIASTOLE is 0.6 to 1.1 cm thick
Myocardium thickness > 1.1 cm –> diagnosis of LVH can be made
List the Risks of Anaesthesia to Hypertensive Patients
- Cardiovascular lability
- Perioperative myocardial ischaemia and arrhythmias
- Perioperative organ dysfunction
What should be considered in the instance of cardiovascular lability
Remifentanyl
Invasive arterial BP monitoring
In patients with HPT what is the intraoperative BP target
Within 20 % of baseline values
Why is it important to maintain BP within 20% of baseline
Hypertension changes autoregulation of organ blood flow around the higher pressure
What additional intra-operative monitoring is appropriate in severe uncontrolled HPT
5 lead ECG with ST analysis
IABP
CVP (Stiff LVH may require adequate preload to maintain SV)
True or false and why: The presence of left ventricular hypertrophy on ECG necessitates echocardiography
Echocardiographic assessment is sought based on the patient’s symptoms and signs and the procedure proposed. An isolated finding of LVH on ECG does not warrant an echo. However, if this is combined with poor exercise tolerance or an ejection systolic murmur, an echo might be required.
How is La Place law applied clinically
Laplace’s law applies to the increased force of contraction and wall tension required to maintain cardiac output in the failing dilated heart.
Classify the causes of heart failure
CARDIAC Ischaemic (2/3rds of cases) Non-ischaemic - Alcohol - Drug-induced - Metabolic - Myocarditis - Genetic - Idiopathic - Peripartum - Valvular heart disease - Restrictive disease - Pericardial - Congenital heart disease
NON-CARDIAC
- Hypertension
- High output states
- Thyroid disease
Define NYHA classification of functional capacity in cardiac patients
1 - No symptoms during ordinary activities
2 - Symptoms with strenuous activity
3 - Comfortable only at rest
4 - Symptoms at rest
How should ejection fraction be interpreted
> 60% - good
30 - 60 % moderate
< 30% poor
When is transoesophageal ECHO useful
- When TTE was suboptimal (obese)
- In patients on mechanical ventilation
- When visualization of posterior structures is required
Other imaging studies
LV function may also be assessed by:
- CT: Cardiac computed tomography (CT) and magnetic 2. MRI: resonance imaging (MRI)
- Angiography: Ventriculography during coronary angiography
- SPECT: Gated single photon emission computed tomography (SPECT)
- MUGA: Multigated acquisition (MUGA) scans
What are the clinical signs that suggest decompensated heart failure
S3
Crackles
Raised JVP
What are the benefits of Five-lead ECG and ST analysis
A 5-lead ECG allows simultaneous monitoring of two different leads. This allows us to monitor both the anterior and inferior aspects of the heart, i.e. the regions which are most susceptible to ischaemia.
ST analysis provides continuous measurement of ST segment depression or elevation, by lead, as positive or negative readings, in millimetres, respectively.
What is the target range for CVP
8 - 12 mmHg
10 - 15 cmH2O
List three methods of cardiac output monitoring
- Pulmonary artery catheter, using thermodilution method
- Transoesphageal Doppler
- Pulse pressure methods (PiCCOTM, LiDCOTM and VigileoTM)
True or false: Urine output is a good guide to peri-operative fluid therapy
Urine output is a poor guide to fluid management during the perioperative period for various reasons, including increased antidiuretic hormone (ADH) secretion.
How should fluid management be guided in the perioperative period
CVP: 8 - 12 (look at trends and response)
Pulse pressure variation
Oesophageal Doppler
Define pulsus paradoxus
Pulsus paradoxus is a phenomenon in which the difference in systolic blood pressure (BP) between inspiration and expiration is more than 10 mmHg.
What is reverse pulsus paradoxus and when does this occur
Reverse pulsus paradoxus — occurs during controlled mechanical ventilation when arterial pressure rises during inspiration and falls during expiration due to changes in intra-thoracic pressure secondary to positive pressure ventilation.
What are other names for reverse pulsus paradoxus
Paradoxical pulsus, respiratory paradox, systolic pressure variation and pulse pressure variation.
What is the formula for Stroke Volume Variation (SVV)
SVV = (SVmax - SVmin)/SVmean over a respiratory cycle
What is the formula for Pulse Pressure Variation (PPV)
PPV = (PPmax - PPmin)/PPmean over a respiratory cycle
