Cardiomyopathy

Dilated cardiomyopathy was the subject of an SAQ in March 2019 (68% pass rate).

The examiners commented on a lack of 'sufficient knowledge or clinical experience to discuss the practicalities of anaesthetizing patients with dilated cardiomyopathy'.

There are separate pages dedicated to peripartum cardiomyopathy and hypertrophic cardiomyopathy.

Resources

Cardiomyopathies are:

myocardial disorders in which the heart muscle is structurally and functionally abnormal, in the absence of a causative cardiac factor sufficient to cause the observed myocardial abnormality

Primary cardiomyopathies arise without extrinsic pathology, though there are many aetiologies of secondary cardiomyopathy

Dilated cardiomyopathy
Peripartum cardiomyopathy
Hypertrophic cardiomyopathy
Restrictive cardiomyopathy
Arrhythmogenic cardiomyopathy
Other cardiomyopathies

Comparison table

Type	Dilated	Peripartum	Hypertrophic	Restrictive	Arrhythmogenic
Gender bias	M>F	F only	Equal	Equal	Equal
Prevalence	0.04-0.4%	0.01-0.1%	0.2%	Rare	0.08%
Aetiology	Up to 40% genetic Various others	Pregnany-induced inflammation Altered prolactin processing	Autosomal dominant	Multiple	Autosomal dominant
Histology	Myocyte hypertrophy Fibrosis Lymphocyte infiltration	Lymphocyte infiltration Myocyte oedema Variable fibrosis	Myocyte fibrosis and disarray 70% have HOCM	Myocyte hypertrophy Fibrosis Lymphocyte infiltration	Replacement of RV myocardium with fibro-fatty tissue
ECG	Normal, or BBB Abnormal ST, T or QT Tachyarrhythmias	As per DCM	LVH Various ST and T-wave abnormalitie	AF VT Sick sinus syndrome Low QRS voltages	Normal (40-50%) R/LBBB TWI Epsilon waves
Prognosis	Aetiology-dependent	Ranges: full recovery to persistent DCM	1% annual mortality	Aetiology-dependent	Depends on risk factors for SCD

The commonest cardiomyopathy, it is defined by LV dilatation and (global or regional) systolic dysfunction (LVEF <50%) ± RV dilatation and dysfunction

Aetiology

Genetic (40%)	Post-myocarditis	Toxic	Endocrine	Nutritional deficiencies	Electrolyte	Autoimmune	Drugs
TTN \| TNNT2	Viral	Ethanol	Hyper-/hypo-thyroidism	Thiamine	Hypocalcaemia	RA	Anti-psychotics
MYH7 \| LMNA	Lyme's disease	Cocaine	Cushing's/Addison's	Selenium	Hypophosphataemia	SLE	Lithium
FLNC \| DSP	Mycobacterial	Amphetamines, ecstasy	Phaeochromocytoma	Zinc/copper		Sarcoidosis	Phenothiazines
BAG3 \| RBM20	Fungal	Iron overload	Acromegaly	Carnitine		Myasthenia	Anti-retrovirals
	Chagas' disease	Steroid use	Diabetes mellitus			IBD	Anti-cancer agents

Pathogenesis

Progressive enlargement of one/both ventricles
Interaction between actin and myosin filaments becomes inefficient, leading to systolic impairment and low stroke volume
The dilated ventricles have a low ratio of wall thickness to diameter
This increases ventricular wall stress and oxygen demand according to Laplace's law, further impairing systolic function

Features

Many patients are asymptomatic, but may present with acutely decompensated heart failure
There is a risk of life-threatening arrhythmia and sudden death, so patients who are symptomatic with LVEF <30% should have an ICD fitted

Management

Address modifiable cardiovascular risk factors
Medical

ACE-I/angiotensin-neprolysin inhibitors
β-blockers
Mineralocorticoid receptor antagonists
SGLT2-inhibitors
Anticoagulation in those with cardiomyopathy-associated atrial fibrillation

Interventional

ICD if previous cardiac arrest, LVEF <35% or high risk genes
Cardiac transplant

Restrictive ventricular physiology in the presence of:

Normal or reduced diastolic volumes, and
Normal or reduced systolic volumes, and
Normal ventricular wall thickness (there may be a small degree of increased thickness e.g. amyloidosis, Fabry's disease)

It is rare in the developed world
Classically have heart failure with preserved ejection fraction, bi-atrial enlargement, bradyarrhythmias ± contractility issues
Worst prognosis of all the cardiomyopathy phenotypes

Aetiologies

Intrinsic myocyte dysfunction	Endomyocardial disorders	Myocardial extracellular matrix disorders
Primary disease	Endomyocardial fibrosis	Hyperoxaluria
Storage disorders	Hypereosinophilia	Amyloidosis \| sarcoidosis
Drugs e.g. chloroquine	Carcinoid syndrome	Radiation or other cancer treatment

An inherited disorder characterised predominantly by RV dilatation and/or dysfunction as the RV myocardium is replaced by fibro-fatty tissue
The principle issue is arrhythmia and risk of sudden cardiac death, especially if:

Young age
Sporting activity
Family history of sudden cardiac death
Impaired RVSF ± LV involvement
History of syncope or arrhythmia

Clinical phases

Phase 1 - concealed

Asymptomatic and sudden death may be the first presentation

Phase 2 - overt

Established structural abnormality; patients experience syncope and arrhythmias

Phase 3 - end stage

Severe structural changes; ventricular dilation and dysfunction

Management

Prevent arrhythmias with:

Avoidance of sports
Frequent or continuous monitoring
Rate control; β-blocker preferred (e.g. sotalol) but amiodarone, flecainide and verapamil other options
ICD insertion
Catheter ablation
Cardiac transplant

Perioperative management of ARVC is covered in this BJA Education from 2018

A transient LV apical ballooning syndrome
Characterised by regional systolic dysfunction, dilatation, and oedema involving the LV apex
Mostly in post-menopausal women, precipitated by emotional or physical distress
Similar phenomenon to neurogenic myocardial stunning e.g. following SAH
Not classified as a true cardiomyopathy as features are typically transient, resolving in days-weeks

Perioperative management of the patient with dilated cardiomyopathy

Represent a challenging cohort of patients owing to the risk of:

Perioperative arrhythmias
Acute congestive heart failure
Embolic events
Perioperative mortality (high risk)

Perioperative management of hypertrophic and peripartum cardiomyopathies is covered on their respective pages

Undertake risk assessment prior to anaesthesia, with an MDT approach

Investigations

Blood tests including BNP levels, to diagnose and assess the severity of heart failure

TTE: assess structural (e.g. valvular) and functional cardiac abnormalities

Cardiac MRI may be useful in assessing aetiology, as it may reveal inflammation, infiltration or fibrosis
Myocardial biopsy may be useful in cases of myocarditis or infiltrative disease e.g. amyloidosis

Optimisation

Treat other comorbidities e.g. hypertension, myocardial ischaemia, smoking

Disease-modifying drugs for HF-rEF, which include:

ACE-inihibitors, or angiotensin receptor antagonists if ACE-inhibitors aren't tolerated

Improve survival, slow disease progression and reduce LOS
No convincing data to suggest a survival benefit from ACE-I/ARA in HF-pEF

β-blockers

Although negatively inotropic, they increase diastolic time and therefore LV filling time
Reduce mortality

Mineralocorticoid receptor antagonists e.g. spironolactone, eplerenone

Arrhythmias should be treated and/or suitable devices implanted prior to surgery e.g. amiodarone, digoxin, PPM, ICD
Anticoagulation e.g. for DCM with an EF <30%

Monitoring and access

AAGBI
Consider 5-lead ECG
A-line
CVC
Consider invasive cardiac output monitoring, including TOE or Oesophageal doppler
BIS may help titration of anaesthetic agents

Haemodynamic goals

Cardiovascular feature	Goal of management
Heart rate and rhythm	Avoid tachycardia Maintain sinus rhythm with rapid treatment of arrhythmia
Preload	Maintain adequate preload / normovolaemia
Afterload	Prevent large increases in SVR Careful titration of anaesthetic agents
Contractility	Avoid negative inotropy and provide inotropic support
Other	Intra-operative correction of deranged electrolytes

Regional anaesthesia

Tends to be a good option for those with dilated cardiomyopathy
Peripheral nerve blocks carry the benefit of minimal haemodynamic changes and analges
Neuraxial anaesthesia:

Advantages	Disadvantages
↓ afterload & therefore ↑ cardiac output	↓ diastolic BP & can ↓ coronary perfusion
↓ risk of tachycardia or ↑ SVR from surgical stimulus	Avoid in HoCM as ↓ preload/afterload + fixed cardiac output state from LVOT obstruction is dangerous
	Treatment of hypotension with fluids ↑ risk of oedema (pulmonary/peripheral)

General anaesthesia

Tends to be better tolerated in HoCM than DCM
Be cautious with induction agents as circulating time is impaired

Agent	Notes
Opioids	Minimal cardiovascular effect Can ↓ required doses of other agents
Propofol	Benefit of reducing SVR Downside of causing negative inotropy
Ketamine	Increases SVR (not suitable for DCM) Beneficial in HoCM & RCM
Etomidate	Least haemodynamic changes Known issues
Volatiles	Cause myocardial suppression in high concentration

Cardiovascular support

Maintain sinus rhythm - low threshold for DCCV if arrhythmia develops
Avoid large volume infusions

Inotropic support

Consider if measured cardiac output and clinical state suggest it is indicated
The patient's normal BP may be significantly lower than the general populations
Milrinone/enoximone, levosimendan, dopamine and dobutamine are options
Use with caution in those with high PCWP (normal 6-12mmHg) as they may worsen LVOT obstruction or MR, leading to pulmonary oedema

Vasopressors

May be beneficial although should avoid increasing afterload too much e.g. in DCM
Are the preferred first line treatment for hypotension in patients with LVOT obstruction e.g. in HoCM

May require exogenous support such as biventricular pacing or IABP

Manage in a suitable post-operative setting e.g. HDU to facilitate continuous cardiac monitoring
Adequate analgesia reduces the deleterious effects of raised SVR
May require IV diuretics or even haemofiltration in the early post-operative period