Morfopatologie.usmf.md



HEART DISEASES

Introduction

Miocardial Infarction

Ischemic Heart disease

Pericarditis

Pericardial Effusion

Hemopericardium

Cardiac tumors

Introduction

Although many diseases can involve the heart and blood vessels, cardiovascular dysfunction results from one or more of five principal mechanisms:

• Failure of the pump. In the most common circumstance, the cardiac muscle contracts weakly or inadequately, and the chambers cannot empty properly. In some conditions, however, the muscle cannot relax sufficiently to permit ventricular filling.

• An obstruction to flow, owing to a lesion preventing valve opening or otherwise causing increased ventricular chamber pressure (e.g., aortic valvular stenosis, systemic hypertension, or aortic coarctation). The increased pressure overworks the chamber that pumps against the obstruction.

• Regurgitant flow causes some of the output from each contraction to flow backward, adding a volume workload to each of the chambers, which must pump the extra blood (e.g., left ventricle in aortic regurgitation; left atrium and left ventricle in mitral regurgitation).

• Disorders of cardiac conduction. Heart block or arrhythmias owing to uncoordinated generation of impulses (e.g., atrial or ventricular fibrillation) lead to nonuniform and inefficient contractions of the muscular walls.

• Disruption of the continuity of the circulatory system that permits blood to escape (e.g., gunshot wound through the thoracic aorta).

OBJECTIVES

You should be able to:

• Briefly define, discuss, differentiate or give the significance of the key words.

• Cite the statistical significance of ischemic heart disease as a cause of death.

• Identify and describe the four clinico-pathologic syndromes of ischemic heart disease (myocardial infarction, angina pectoris, congestive heart failure and sudden cardiac death). Define and describe each.

• Correlate the region of infarction in the LV with the coronary artery occluded.

• List the major complications of myocardial infarction and relate them to changes in the tissue.

• Relate the degree of risk of myocardial infarction to the number and severity of risk factors.

• List four possible etiologies for myocarditis. Which is the most common?

• List the major causes of pericarditis, of hemopericardium.

• Explain the mechanism of death in cardiac tamponade.

• Discuss a patient who has an enlarged heart by chest x-ray and an electrocardiogram shows evidence of left ventricular hypertrophy. What are the five general categories of heart disease which might give this picture? Which are common? Which are uncommon? What simple examinations or maneuvers could you make clinically to narrow the differential diagnosis? Would the age of the patient make a difference?

• Explain why mural thrombi are features of congestive cardiomyopathy, mitral stenosis, ventricular aneurysm, and abdominal aortic aneurysm?

• Explain why cardiac amyloidosis causes a restrictive cardiomyopathy? With what conditions is amyloid associated?

• Tell whether the most common tumors of the heart are primary or metastatic?

• List the three most common metastatic tumors to the heart and/or pericardium?

• Name the most common primary tumor of the heart.

• Discuss the following: a left atrial myxoma may prolapse into the mitral valve. What would this do to cardiac output? What symptomatology could result?

KEY WORDS:

Ischemia, hypoxia, stenosis vs. occlusion, infarct, complications of myocardial infarct (rupture of papillary muscle, ventricular or septal myocardial rupture, mural thrombus, ventricular aneurysm, arrhythmia, heart failure, sudden death), collaterals, vasospasm, coronary insufficiency, angina pectoris, cardiogenic shock, lactic dehydrogenase (LDH), creatine kinase (CK), MB band, troponin. Myocarditis (infective, toxic, hypersensitivity), cardiomyopathy (hypertrophic, congestive, restrictive), alcoholic cardiomyopathy, cardiac amyloidosis, pericarditis (constrictive, fibrinous, suppurative, tumor, uremic), pericardial effusion.

LABORATORY OBJECTIVES

Be sure you can answer the following:

• What are the major sites of coronary atherosclerosis?

• What changes occur in the epicardium and endocardium overlying an area of infarction and what is their significance?

• Remember the heart is a muscle with both contractile strength and automaticity. Why do some patients with a myocardial infarct have pump failure while other have arrhythmias?

• At what intervals following infarct is the myocardium most susceptible to rupture or aneurysm formation and why?

• By what two mechanisms does a left ventricular aneurysm interfere with the pump's function?

Heart Failure

The abnormalities described above often culminate in heart failure, an extremely common result of many forms of heart disease. In heart failure, often called congestive heart failure (CHF), the heart is unable to pump blood at a rate commensurate with the requirements of the metabolizing tissues or can do so only at an elevated filling pressure. Although usually caused by a slowly developing intrinsic deficit in myocardial contraction, a similar clinical syndrome is present in some patients with heart failure caused by conditions in which the normal heart is suddenly presented with a load that exceeds its capacity (e.g., fluid overload, acute myocardial infarction, acute valvular dysfunction) or in which ventricular filling is impaired (see below). CHF is a common and often recurrent condition with a poor prognosis.

LEFT-SIDED HEART FAILURE

As discussed, left-sided heart failure is most often caused by (1) ischemic heart disease, (2) hypertension, (3) aortic and mitral valvular diseases, and (4) nonischemic myocardial diseases. The morphologic and clinical effects of left-sided CHF primarily result from progressive damming of blood within the pulmonary circulation and the consequences of diminished peripheral blood pressure and flow.

Morphology. The findings in the heart vary depending on the cause of the disease process; abnormalities such as myocardial infarction or a valvular deformity may be present. Except with obstruction at the mitral valve or other processes that restrict the size of the left ventricle, this chamber is usually hypertrophied and often dilated, sometimes quite massively. There are usually nonspecific changes of hypertrophy and fibrosis in the myocardium. Secondary enlargement of the left atrium with resultant atrial fibrillation (i.e., uncoordinated, chaotic contraction of the atrium) may either compromise stroke volume or cause blood stasis and possible thrombus formation (particularly in the atrial appendage). A fibrillating left atrium carries a substantially increased risk of embolic stroke.22 The extracardiac effects of left-sided heart failure are manifested most prominently in the lungs, although the kidneys and brain may also be affected.

Lungs. Pressure in the pulmonary veins mounts and is ultimately transmitted retrograde to the capillaries and arteries. The result is pulmonary congestion and edema, with heavy, wet lungs as described in detail in Chapters 4 and 15. It is sufficient to note here that the pulmonary changes include, in sequence, (1) a perivascular and interstitial transudate, particularly in the interlobular septa, responsible for Kerley's B lines on x-ray; (2) progressive edematous widening of alveolar septa; and (3) accumulation of edema fluid in the alveolar spaces. Moreover, iron-containing proteins in edema fluid and hemoglobin from erythrocytes, which leak from congested capillaries, are phagocytosed by macrophages and converted to hemosiderin. Hemosiderin-containing macrophages in the alveoli (called siderophages, or heart failure cells) denote previous episodes of pulmonary edema.

These anatomic changes are associated with striking clinical manifestations. Dyspnea (breathlessness), usually the earliest and the cardinal complaint of patients in left-sided heart failure, is an exaggeration of the normal breathlessness that follows exertion. With further impairment, there is orthopnea, which is dyspnea on lying down that is relieved by sitting or standing. Thus the orthopneic patient must sleep while sitting upright. Paroxysmal nocturnal dyspnea is an extension of orthopnea that consists of attacks of extreme dyspnea bordering on suffocation, usually occurring at night. Cough is a common accompaniment of left-sided failure.

Kidneys. Decreased cardiac output causes a reduction in renal perfusion, which activates the renin-angiotensin-aldosterone system, inducing retention of salt and water with consequent expansion of the interstitial fluid and blood volumes. This compensatory reaction can contribute to the pulmonary edema in left-sided heart failure and is counteracted by the release of ANP through atrial dilation, which acts to decrease excessive blood volume. If the perfusion deficit of the kidney becomes sufficiently severe, impaired excretion of nitrogenous products may cause azotemia, in this instance prerenal azotemia

Brain. In far-advanced CHF, cerebral hypoxia may give rise to hypoxic encephalopathy (see Chapter 28), with irritability, loss of attention span, and restlessness, which may even progress to stupor and coma

RIGHT-SIDED HEART FAILURE

Isolated right-sided heart failure occurs in only a few diseases. Usually it is a secondary consequence of left-sided heart failure because any increase in pressure in the pulmonary circulation incidental to left-sided heart failure inevitably produces an increased burden on the right side of the heart. The causes of right-sided heart failure must then include all those that induce left-sided heart failure.

Pure right-sided heart failure most often occurs with chronic severe pulmonary hypertension and thus is called cor pulmonale. In this condition, the right ventricle is burdened by a pressure workload due to increased resistance within the pulmonary circulation. Hypertrophy and dilation are generally confined to the right ventricle and atrium, although bulging of the ventricular septum to the left can cause dysfunction of the left ventricle.

The major morphologic and clinical effects of pure right-sided heart failure differ from those of left-sided heart failure in that pulmonary congestion is minimal, whereas engorgement of the systemic and portal venous systems may be pronounced.

Morphology. Liver and Portal System. The liver is usually increased in size and weight (congestive hepatomegaly), and a cut section displays prominent passive congestion (see Chapter 18). Congested red centers of the liver lobules are surrounded by paler, sometimes fatty, peripheral regions. In some instances, especially when left-sided heart failure is also present, the severe central hypoxia produces centrilobular necrosis along with the sinusoidal congestion. With long-standing severe right-sided heart failure, the central areas can become fibrotic, creating so-called cardiac sclerosis or cardiac cirrhosis

Right-sided heart failure also leads to elevated pressure in the portal vein and its tributaries. Congestion produces a tense, enlarged spleen (congestive splenomegaly). Microscopically there may be marked sinusoidal dilation. With long-standing congestion, the enlarged spleen may achieve a weight of 300 to 500 gm (normal, approximately 150 gm). Chronic edema of the bowel wall can also occur and in some patients may interfere with absorption of nutrients. In addition, accumulations of transudate in the peritoneal cavity may give rise to ascites.

Kidneys. Congestion of the kidneys is more marked with right-sided heart failure than with left-sided heart failure, leading to greater fluid retention, peripheral edema, and more pronounced azotemia.

Brain. Symptoms essentially identical to those described in left-sided heart failure may occur, representing venous congestion and hypoxia of the central nervous system.

Pleural and Pericardial Spaces. Accumulation of fluid in the pleural space (particularly right) and pericardial space (effusions) may appear. Thus, while pulmonary edema indicates left-sided heart failure, pleural effusions accompany right-sided heart failure. Pleural effusions can range from 100 ml to well over 1 liter and can cause partial atelectasis of the corresponding lung.

Subcutaneous Tissues. Peripheral edema of dependent portions of the body, especially ankle (pedal) and pretibial edema, is a hallmark of right-sided heart failure. In chronically bedridden patients, the edema may be primarily presacral. Generalized massive edema is called anasarca.

Ischemic Heart Disease

Ischemic heart disease (IHD) is the generic designation for a group of closely related syndromes resulting from myocardial ischemia-an imbalance between the supply (perfusion) and demand of the heart for oxygenated blood. Ischemia comprises not only insufficiency of oxygen, but also reduced availability of nutrient substrates and inadequate removal of metabolites (see Chapter 1). Isolated hypoxemia (i.e., diminished transport of oxygen by the blood) induced by cyanotic congenital heart disease, severe anemia, or advanced lung disease is less deleterious than ischemia because perfusion (including metabolic substrate delivery and waste removal) is maintained.

The clinical manifestations of IHD can be divided into four syndromes

• Myocardial infarction (MI), the most important form of IHD, in which the duration and severity of ischemia is sufficient to cause death of heart muscle.

• Angina pectoris, in which the ischemia is less severe and does not cause death of cardiac muscle. Of the three variants-stable angina, Prinzmetal angina, and unstable angina-the latter is the most threatening as a frequent harbinger of MI.

• Chronic IHD with heart failure.

• Sudden cardiac death.

Myocardial Infarction

DEFINITION

• Localized coagulative necrosis of myocardium

• Caused by vascular occlusion, or decreased flow

ETIOLOGY AND PATHOGENESIS

• Atherosclerosis of coronary arteries (99% of MI's

• Transmural MIs usually have cracked plaque and occlusive thrombus

• Decreased supply (fixed atherosclerotic stenosis, coronary mural thrombosis, and/or vasospasm, e.g.)

• Increased O2 demand (eg., LVH due to hypertension or aortic stenosis)

III. EPIDEMIOLOGY

• Basically, same as that of atherosclerosis

• M:F::2-6:1

IV. DISTRIBUTION AND PATTERNS

• LAD --> antero-septal LV

• LCX --> lateral LV

• RCA --> posteroseptal LV

• RV infarcts less common, usually extensions of large posterior LV infarcts

MORPHOLOGY OF MYOCARDIAL INFARCTS

| MYOCARDIAL INFARCTION--PATHOLOGIC FEATURES AND COMPLICATIONS |

| STAGE: |Early Acute |Acute |Organizing |Old |

|Duration: |6-24 hrs. |1-6 days |1 wk.-3 wks. |3 mos. or longer |

|Gross: |Subtle: patchy pallor, slight |Obvious pale, yellow |Red-brown edge, around pale |Firm, white scar, |

| |hyperemia | |center |contracted, wall thinned |

|Micro: |Thin wavy fibers, |Necrotic myocytes, many PMNs |Granulation tissue, acute |Collagen, thinning of |

| |eosinophilia, few PMNs | |and/or chronic inflammation |wall |

| COMPLICATIONS |

|Dysrhythmia | ++++ |++ |++ |+(possible any time) |

|Mural thrombus |- |++ |++ |+ |

|Pericarditis |- |+ |++ |fibrous |

|Rupture |- |++++ |- |- |

|LV Aneurysm |- |+ |+++ |++ |

|Heart Failure |+ |++ |++ |++ |

| Note: These histologic features of of a classical importance and of interest to autopsy pathologists. In practice, the lesions vary |

|considerably. Think through the four stages and relate the gross and histologic findings to the complications. |

• Transmural vs. Subendocardial

• Heal from outside

• Four stages, as follows:

| TIME |PATHOLOGIC STAGE |MICROSCOPIC |GROSS |

| 6-24 hrs. | Early acute |eosinophilia, wavy fibers, few or no PMNs |barely visible, mild wall |

| | | |stretching |

| 1-7 days | Acute |coagulative necrosis , lots of PMNs |yellow, wall thinning  |

| 1 wk.-3 mos. | Organizing |granulation tissue border |red-brown edge around yellow |

| | | |center, wall thinning |

| 3 mos.-->yrs. | Old |collagen |white scar, wall thinning  |

Morphology. Myocardial infarcts less than 12 hours old are usually not apparent on gross examination. It is often possible, however, to highlight the area of necrosis that first becomes apparent after 2 to 3 hours after the infarct, by immersion of tissue slices in a solution of triphenyltetrazolium chloride (TTC). This histochemical stain imparts a brick-red color to intact, noninfarcted myocardium where the dehydrogenase enzymes are preserved. Because dehydrogenases are depleted in the area of ischemic necrosis (they leak out through the damaged cell membranes), an infarcted area is revealed as an unstained pale zone (while old scarred infarcts appear white and glistening). Subsequently, by 12 to 24 hours, an infarct can be identified in routinely fixed gross slices owing to a red-blue hue caused by stagnated, trapped blood. Progressively thereafter, the infarct becomes a more sharply defined, yellow-tan, somewhat softened area that by 10 days to 2 weeks is rimmed by a hyperemic zone of highly vascularized granulation tissue. Over the succeeding weeks, the injured region evolves to a fibrous scar.

Using light microscopic examination of routinely stained tissue sections, the typical changes of coagulative necrosis become detectable variably in the first 4 to 12 hours. "Wavy fibers" may be present at the periphery of the infarct; these changes probably result from the forceful systolic tugs by the viable fibers immediately adjacent to the noncontractile dead fibers, thereby stretching and buckling them. An additional but sublethal ischemic change may be seen in the margins of infarcts: so-called vacuolar degeneration or myocytolysis, involving large vacuolar spaces within cells, probably containing water.

This potentially reversible alteration is particularly frequent in the thin zone of viable subendocardial cells. Subendocardial myocyte vacuolization in other contexts may signify severe chronic ischemia.

The necrotic muscle elicits acute inflammation (typically most prominent at 2 to 3 days).

Thereafter macrophages remove the necrotic myocytes (most pronounced at 5 to 10 days), and the damaged zone is progressively replaced by the ingrowth of highly vascularized granulation tissue (most prominent at 2 to 4 weeks), which progressively becomes less vascularized and more fibrous. In most instances, scarring is well advanced by the end of the sixth week, but the efficiency of repair depends on the size of the original lesion. As healing requires the participation of inflammatory cells that migrate to the region of damage through intact blood vessels, which often survive only at the infarct margins, the infarct heals from its borders toward the center. Thus, a large infarct may not heal as readily nor as completely as a small one. A healing infarct may appear nonuniform, with the most advanced healing at the periphery. Once a lesion is completely healed, it is impossible to distinguish its age (i.e., the dense fibrous tissue scar of an 8-week-old and a 10-year-old lesion may look similar).

Several infarcts of varying age are frequently found in the same heart. Repetitive necrosis of adjacent regions yields progressive extension of an individual infarct over a period of days to weeks. Examination of the heart in such cases often reveals a central zone of repairing infarct that is days to weeks older and whose healing is more advanced than that of a peripheral margin of more recent ischemic necrosis. This contrasts with the appearance of a single-event infarct described above, in which the most advanced repair was peripheral. An initial infarct may extend because of retrograde propagation of a thrombus, proximal vasospasm, progressively impaired cardiac contractility that renders flow through moderate stenoses critically insufficient, the development of platelet-fibrin microemboli, the appearance of an arrhythmia that impairs cardiac function, or poor perfusion owing to progressively impaired myocardial function. In general, the sequential morphology of evolving subendocardial and transmural infarcts is qualitatively similar, but subendocardial infarcts tend to be smaller.

COMPLICATIONS

• May heal fully without complications

• Complications (incidence, 5% of MIs)

o Rupture (free wall, septum, or papillary muscle)

o Mural thrombus (cause of sytemic embolism)

o Congestive heart failure (CHF) (to review CHF, click here; Adaptive Changes/Heart Failure)

o LV Aneurysm

o Dysrhythmia, arrhythmia

o Pericarditis (if transmural involvement)

o Pulmonary thromboembolism (venous congestion --> thrombosed leg vein)

CLINICAL SYNDROMES

• Four major syndromes of Ischemic Heart Disease

o Angina pectoris

o MI

o CHF (ischemic cardiomyopathy)

o Sudden Cardiac Death (SCD)

• Angina pectoris

o Precordial chest pain

o Typical -- fixed atherosclerotic lesions

▪ brought on by exertion

▪ relieved by rest and nitroglycerin (NTG)

▪ radiates to L arm or neck (less common: back, right arm, abdomen)

o Atypical angina-- cracked plaques

▪ not related to exertion

▪ due to vasospasm, or cracked plaque

o Differential diagnosis -

• Myocardial Infarction-- crushing chest pain

• Congestive Heart Failure-- weakness, fatigue, SOB, PND

o Findings: large dilated LV, low cardiac output (C.O.), pulmonary and/or visceral congestion

o Mechanisms: 3-vessel disease with multiple MIs or diffuse interstitial scarring

• Sudden cardiac death - due to dysrtythmia, usually vent. fib. (big hearts die in v. fib.)

MYOCARDIAL & PERICARDIAL DISEASES, AND CARDIAC TUMORS

Pericardial Disease

PERICARDITIS

• Inflammation of the pericardium

• Types and (in parentheses) Causes

o Fibrinous (MI, uremia)

o Purulent (Staphylococcus)

o Granulomatous (TB)

o Hemorrhagic (tumor, TB, uremia)

o Fibrous (a.k.a.Constrictive) (arises from any of above)

PERICARDIAL EFFUSION

• Serous fluid in pericardial sac

• Usual cause: CHF

III. HEMOPERICARDIUM

• Myocardial rupture from MI

• Trauma

• Bleeding from organizing fibrinous pericarditis of any cause (infection, tumor, etc.)

• Dissecting aortic hemorrhage, retrograde into sac

Cardiac Tumors

PRIMARY TUMORS

Rare, but most common by far is left atrial myxoma

• Arise from interatrial septum, mostly in LA, often on a stalk

• Can prolapse through MV into LV, cause CHF

• Can embolize, cause stroke, etc.

 

 

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