CARDIOMYOPATHIES

CARDIOMYOPATHIES

Joseph June 11, 2013

Readings:

Stoelting Ch. 8 pp 149-154

M&M 418-419

n  Definition of MYOPATHY:

   Any disease or abnormal condition of

   STRIATED MUSCLE.

   CARDIOMYOPATHY is a disease of the myocardium, primarily due to primary disease of the heart muscle.

There are various types of CARDIOMYOPATHIES

n  DILATED CARDIOMYOPATHY (congestive)

n  NONDILATED CARDIOMYOPATHY (restrictive)

n  HYPERTROPHIC CARDIOMYOPATHY

n  The classifications of cardiomyopathies are based on the LEFT VENTRICLE ejection fraction and ventricular volume (via ECHO or radionuclide studies of the ventricle)

             

n  Cardiomyopathies are disorders that directly affect either the right or left VENTRICLE resulting in CONGESTIVE HEART FAILURE.

n  The interesting thing about congestive heart failure related to cardiomyopathy is that the CHF cannot be attributed to CAD, any valve disease, pericardial disease, or even HTN.

DILATED CARDIOMYOPATHY

The ETIOLOGY is said to be idiopathic.

Specific etiologies include nutritional deficits, alcohol abuse, infections (viral, bacterial, and parasitic) causing myocarditis.

PATHOPHYSIOLOGY:

n  In order to maintain stroke volume as myocardial contractility progressively declines, LVEDP increases and the heart DILATES (Frank Starling mechanism).

n  Compensatory mechanisms in addition to cardiac enlargement include tachycardia to maintain CO and elevations in SVR to sustain blood pressure.

HEMODYNAMIC CHARACTERISTICS:

n  Marked decrease in LVEF (<0.4)

n  Marked increase in ventricular volume

n  Normal to increased ventricular filling pressures

n  Normal to decrease stroke volume

n  Cardiac output may be normal to low

n  Left atrial pressures may be normal to high

n  Ventricular dilation may be so MARKED that mitral or tricuspid regurgitation occurs.

n  EKG changes that you might see include LEFT BBB and evidence of  left ventricular hypertrophy, ST-segment and T wave abnormalities probably will be present.

n  PVCs and A fib may also be seen.

n  If there are Q waves, this may be indicative of a previous MI.

n  CXR will show pulmonary HTN and biventricular cardiac enlargement.

n  Mural or wall thrombi are likely to form in chambers of the heart that both dilated and hypokinetic.

n  It has been found that there is a HIGH incidence of systemic embolization in these patients (anticoagulation is NOT of proven benefit).

n  The clinical course of patients with dilated cardiomyopathy is characterized by intermittent CHF and systemic embolization.

n  Angina may be prominent in some of these patients.

n  The prognosis of these patients is POOR.

n  Sudden death may be attributed to acute cardiac dysrhythmias.

n  The most common cause of death is due to CHF

CLINICAL PRESENTATION:

n  Symptoms of right, left, or bi-ventricular failure include extreme fatigibility, marked decrease in exercise tolerance, and DOE or at rest.

n  Episodes of acute pulmonary edema may occur.

n  Common signs include JVD, hepatomegaly, peripheral edema, ascites, S3 gallop, and murmur of mitral insufficiency

n  Medications include digitalis, diuretics, and vasodilators.

n  Anti-arrhythmics are prescribed and regulated most effectively by 24-hour Holter monitor recordings.

n  Beta blockers and disopyramide are AVOIDED because of the likelihood of inducing further congestive failure.

ANESTHETIC IMPLICATIONS:

n  The MAIN GOAL is to optimize myocardial performance while providing adequate anesthetic depth.

n  Light premedication

n  Inhalationals should be avoided due to the cardiac depressant effects (this is not to say that they can’t be used in low doses)

n  A pure narcotic-oxygen technique offers the advantages of dense analgesia with minimal cardiac depression.

n  As much as possible, optimize ventricular performance.

n  Inotropic agents are required

n  Afterload reduction with nipride, hydralazine, or amrinone will often augment cardiac output.

n  Intraop hypotension is best treated with ephedrine

n  Alpha adrenergic stimulation by phenylephrine could produce adverse increases in ventricular afterload due to elevation of SVR

n  If preload optimization, inotropic support, and afterload reduction are inadequate, the insertion of an IABP should be considered.

n  And obviously a Swan-Ganz catheter is indicated for all of these patients undergoing general anesthesia.

n  If possible, regional anesthesia may be an attractive alternative to general anesthesia.

n  Epidural anesthesia produces changes in preload and afterload that mimic pharmacologic goals in the treatment of this disease.

n  A regional technique may not be the choice is a higher block is indicated.

NONDILATED (RESTRICTIVE) CARDIOMYOPATHY

n  Resembles constrictive pericarditis being characterized by marked increases in ventricular filling pressures, and often with reductions in CO.

n  Signs of right heart failure (hepatosplenomegaly and ascites) predominate.

n  The myocardium is non-compliant and diastolic filling is impeded, reflecting infiltration of the myocardium by abnormal material.

n  This disease can result from infiltrative diseases such as amyloidosis, hemochromatosis or glycogen storage diseases.

n  There is no effective treatment and death is usually due to cardiac dysrhythmias or irreversilble CHF.

n  Hemodynamic characteristics include:

n  Normal to decreased LVEF

n  Normal to decreased ventricular volume

n  Marked increase in ventricular filling pressures

n  Normal to decreased stroke volume

n  Management of anesthesia is similar to that for patients with cardiac tamponade.

n  General anesthesia and positive pressure ventilation is acceptable.

n  Induction and maintenance of anesthesia are often with ketamine, etomidate, and BNZ

n  Anesthetic-induced reductions in myocardial contractility, SVR, and HR must be avoided.

n  Ketamine tends to increase contractility, SVR, and HR.

n  Infusions of catecholamines such as isoproterenol, dopamine, and dobutamine may be required to maintain cardiac contractility.

HYPERTROPHIC CARDIOMYOPATHY (IHSS)

n  Also known as IHSS (idiopathic hypertrophic subaortic stenosis .

n  Currently, the preferred term is HYPERTROPHIC CARDIOMYOPATHY with or without LEFT VENTRICULAR OUTFLOW OBSTRUCTION.

n  A genetically transmitted disease.

n  The myocardial defect is related to the contractile mechanism (an increase in the density of calcium channels that gives rise to myocardial hypertrophy).

n  Assymetrical hypertrophy of the interventricular septum of the left ventricle occurs.

n  This causes a LEFT outflow tract obstruction, and therefore the hemodynamic consequences are similar to those that are characteristic of AORTIC STENOSIS.

n  The most common cause of SUDDEN DEATH in the pediatric and young adult population (eg. Athletes).

HEMODYNAMIC CHARACTERISTICS:

n  Marked increase in LVEF

n  Marked decrease in ventricular volume

n  Normal to increased ventricular filling pressures

n  Normal to increased stroke volume

PATHOPHYSIOLOGY:

n  Left ventricular myocytes are hypertrophic and their arrangement is chaotically arranged and in dissaray.

n  The walls of the coronary arteries are narrowed due to the presence of collagen

n  Diastolic compliance is reduced because the myocardium is stiffer than normal.

n  Ventricular filling pressures are usually elevated and vary markedly with small changes in ventricular volume.

n  Remember that ATRIAL systole may account for 40 to 50 percent of ventricular filling

n  Left ventricular function (LVEF) is supernormal and EFs of 80% are common.

n  The hypercontractility often results in cavitary obliteration during systole.

n  The rapid acceleration of blood traveling through the narrowed ventricular outflow tract creates a VENTURI EFFECT which pulls the anterior mitral valve leaflet into the outflow tract.

n  The anterior mitral valve leaflet further obstructs the left ventricular outflow.

n  Hypertrophic cardiomyopathy with obstruction is affected by three hemodynamic parameters.

n  These three parameters include preload, afterload, and contractility.

n  Increasing contractility exacerbates the obstruction by increasing septal wall contraction and decreasing CO.

n  Increased blood flow velocity causes a greater degree of systolic anterior motion of the mitral valve’s anterior leaflet, creating further obstruction.

n  Decreased preload changes the left ventricular geometry and brings the anterior leaflet of the mitral valve into closer proximity of the hypertrophied septum.

n  Increases in left ventricular contractility cause the LV to empty more completely and increase the degree of septal contractility, which results in a greater degree of obstruction.

CLINICAL PRESENTATION:

n  Chest pain, dyspnea, and exercise induced syncope.

n  EKG: LVH, Q waves, PACs, PVCs, supraventricular or ventricular tachycardia or fibrillation.

n  Treatment is directed at relief of symptoms, control of arrhythmias, and improvement of diastolic relaxation.

n  The arterial pressure waveform in patients with HC may be bifid or bisferiens pulse (2 beat pulse).

n  The initial rapid peak represents early un-obstructed ventricular ejection, while the subsequent decrease and second peak are due to dynamic obstruction.

PULSUS BISFERIENS

ANESTHETIC CONSIDERATIONS:

n  GOALS: preservation of adequate ventricular volume and prevention of left ventricular outflow obstruction.

n  Maintain LV preload by preventing hypovolemia and maintaining NSR.

n  Maintain left ventricular afterload

n  Reduce contractility

n  Adequate or slightly elevated left ventricular volume should be maintained.

n  Avoid decreased venous return (interferes with adequate preload)

n  Avoid increases in myocardial contractility.

n  Inadequate anesthesia results in SNS stimulation and this may be detrimental to the patient (hyperdynamic shifts)

n  In the event of hypotension, adequate perfusion should be maintained by increasing preload with fluids and increasing SVR with phenylephrine.

n  Pharmacologic agents used to treat patients with HC (beta blockers, calcium channel blockers) should be continued until the time of surgery.

n  Beta blockers can be used intraop to reduce HR and contractility.

n  Anesthetic management needs to focus on maintaining LV preload, decreasing contractility, and maintaining SVR.

n  Regional anesthesia can be a consideration in these patients

n  Treat hypovolemia immediately

n  Deep general anesthesia is preferred

n  Because Halothane is the most potent myocardial depressant inhaled agent in use today, it is the ideal choice of all the agents.

n  The PCWP  should be maintained 18-25 mm Hg.

n  If the hemodynamic status deteriorates and exaccerbation of outflow obstruction is suspected, labetalol or propanolol should be given.

CARDIOMYOPATHIES AND OTHER CONDITIONS

TYPE I DIABETES MELLITUS:

n  Patients with DM I may develop cardiomyopathy even in the absence of CAD.

n  Pathologic studies of the heart in patients with DM I who develop cardiomyopathy reveal

n  1. microvascular disease

n  2. hyaline thickening in the coronary arteries

n  3. fibrosis, degeneration, and fragmentation of

       myocytes.

n  The above changes are responsible  for diminished left ventricular compliance and ejection fraction.

HEART TRANSPLANTATION AND CARDIOMYOPATHY:

n  For those individuals in need of cardiac transplantation, idiopathic dilated cardiomyopathy (which is their underlying cause of CHF) accounts for 43% of all cardiac transplant candidates.