Page 265 - ACCCN's Critical Care Nursing

242 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

with HCM is diastolic rather than systolic as in DCM. The patient with HCM deteriorates and is hospitalised, posi-
hypertrophy is not a compensatory response to excessive tive inotropes, chronotropes and nitrates worsen LVOTO
load, such as in aortic stenosis or hypertension. Left ven- and should be avoided. However, beta-adrenergic block-
tricular hypertrophy of variable patterns is seen, occasion- ers, amiodarone and calcium antagonists such as verapra-
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ally with disproportionate septal hypertrophy, which mil are indicated. Due to the familial nature of HCM,
causes left ventricular outflow tract obstruction (LVOTO) relatives aged 12–18 years also need to be screened
in which HCM progresses to hypertrophic obstructive for HCM.
cardiomyopathy, or HOCM. In HCM the muscle mass is
large and hypercontractile, but the left ventricular cavity RESTRICTIVE CARDIOMYOPATHY
is small. The increase in left ventricular systolic pressure Restrictive cardiomyopathies (RCMs) limit diastolic dis-
and the altered relaxation cause diastolic dysfunction tensibility or compliance of the ventricles. The stiff ven-
and impaired ventricular filling. Mitral regurgitation is tricular walls feature diastolic dysfunction and there is
common. These abnormalities combine to produce impaired ventricular filling. Infiltrates into the intersti-
pulmonary congestion and dyspnoea due to a raised end- tium and the replacement of normal myocardium with
diastolic pressure. Sudden cardiac death, often after exer- abnormal tissue hamper this relaxation. Initially, sys-
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tion or other increases in contractility, is sometimes seen tolic function and wall thickness are normal. However, as
in HCM and is thought to be partly attributable to outflow the disease progresses systolic dysfunction occurs. RCM
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obstruction. It is the most common cause of death in is commonly caused by myocardial infiltration, as in
athletes. 63
amyloidosis, sarcoidosis, fibrosis or cardiac metastases, or
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may be idiopathic. Endomyocardial disease is more
Diagnosis common in tropical countries, but in the Western world,
Echocardiography will confirm the presence and pattern RCMs are the least common form of cardiomyopathy. 88
of hypertrophy and the presence (or absence) of an
outflow tract gradient. Examination findings include car- Diagnosis
diomegaly and pulmonary congestion. An S4 heart sound Clinically there is heart failure (increase in JVP, dyspnoea,
is common, and the ECG shows left ventricular hypertro- S3 and S4 heart sounds, and oedema), particularly right
phy and often ventricular arrhythmias. When the obstruc- ventricular, and infiltration of the conduction system may
tive form (HOCM) is present, a systolic murmur, mitral cause conduction defects and heart block. Low-voltage
regurgitation murmur and deep narrow Q waves on ECG, ECGs are commonly seen. Patients commonly present
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may be present. The majority of patients are asymptom- with decreased exercise tolerance due to the impaired
atic and when they present to hospital it will be in severe ability to increase heart rate and cardiac output because of
symptoms of dyspnoea, angina and syncope. Angina is reduced ventricular filling. Restrictive cardiomyopathy
the result of an imbalance between oxygen supply and must be distinguished from constrictive pericarditis (which
demand due to the increased myocardial mass and not it may closely resemble), as pericarditis may be easily
due to atherosclerosis. managed. If echocardiography demonstrates a restrictive
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pattern then a myocardial biopsy may be undertaken to
Management determine its aetiology, especially in the case of systemic
Treatment for HCM is aimed at the prevention of sudden infiltrative disease. 88
cardiac death and pharmacotherapy to increase diastolic
filling and to reduce the LVOTO. Pharmacotherapy Management
includes beta-adrenergic blocker or calcium channel There is no treatment for RCM so the aim of therapy is
blocker therapy, as these decrease contractility and lessen to relieve symptoms. This includes diuretics, corticoste-
outflow tract obstruction. Care is necessary with medica- roids and pacing. The use of nitrates should be done with
tion selection, as vasodilation may worsen obstruction, caution as the filling defect can be worsened by decreased
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causing haemodynamics to suffer. The impact of atrial venous return or hypovolaemia. Generally, prognosis is
fibrillation, by worsening the ventricular filling defect, poor with many dying within 1–2 years of diagnosis. 92
can be dramatic in HCM patients and will require antiar-
rhythmics and anticoagulation. If ventricular arrhythmias HYPERTENSIVE EMERGENCIES
are present, or there is a family history of sudden cardiac
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death, treatment with an ICD should be considered. For Acute, uncontrolled hypertension is often divided into
severely symptomatic patients or those worsening despite two categories: hypertensive emergencies and hyperten-
maximal drug treatment, surgical myectomy to reduce sive urgencies. In hypertensive emergencies blood pres-
the size of the septum and lessen obstruction may be sure needs to be reduced within one hour to prevent
necessary and can result in a marked improvement of end-organ damage, such as hypertensive encephalopathy,
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symptoms. Septal ablation with alcohol injected into papilloedema or aortic dissection. Immediate blood
the first septal branch of the left anterior descending pressure reduction with IV agents under critical care moni-
artery is a less invasive alternative, a procedure that is toring is needed. By contrast, hypertensive urgencies are
usually undertaken with pacemaker insertion as AV block those in which end-organ damage is not occurring, and
is produced. Although surgical myectomy remains the although prompt management is required, this can be
gold standard, both treatments provide effective symptom approached more gradually with oral antihypertensive
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relief and improvement in heart failure severity. If the agents under close supervision, without necessarily