Heart

The heart is an important organ. It moves the blood around. For orthopods, it gets the Ancef (cefazolin) to the bones. When it stops for an extended time... people end-up in the morgue or being seen by a pathologist for an autopsy.

An introduction to cardiovascular pathology is found in the cardiovascular pathology article.

Obscure anatomy

Main article: Heart anatomy

Heart dissection

General rule

• Open along the lines of flow.

Note:

• Don't open RA SVC to IVC - Why? A.: You cut through the territory of the SA node.

Right atrium

• Open along crista terminalis (where the pectinate muscles end).
  • Open right auricle at the same time.

Right ventricle

• Make cut throught the apex (transverse/biventicular section).
• Open along lateral edge (from RA cut).

Right ventricular outflow tract

• Cut along pulmonary artery.

Left atrium

• Isolate the four pulmonary veins - cut 'em so they are long on the heart.
• Join the pulmonary veins on the right with a cut.
• Join the pulmonary veins on the left with a cut.
• Open the posterior aspect of the LA by joining the two previous cuts.
• Open the left auricle (to look for thrombus).

Left ventricle

• Open on the lateral aspect with a long knife.

Left ventricular outflow tract

• Cut the aorta.
  • Avoid cutting the pulmonary artery.
  • Go between the left coronary cusp and right coronary cusp. (???)

Hardware

• Defibrillator - thick wires.
• Pacer - thin wires.

Standard measures

• Mass (weight).
• Left ventricle (LV) - 2 cm below the MV.
• Right ventricle (RV) - 2 cm below the TV.
• Aortic valve (AV) circumference.
• Mitral valve (MV) circumference.
• Pulmonic valve (PV) circumference.
• Tricuspid valve (TV) circumference.

Standard sections

Minimalist approach:

1. LV and PPM (left ventricle and posterior papillary muscle).
2. VL and APM (left ventricle and anterior papillary muscle).

Make the lab work hard approach:

1. PRV (post. RV) with tricuspid valve.
2. ARV (ant. RV) with pulm. valve.
3. PLV (post. LV) with mitral valve.
4. ALV (ant. LV) with aortic valve.
5. Lat. LV.
6. LV and PPM.
7. Post. septum.
8. Mid. septum.
9. Ant. septum.
10. Ant. LV wall.
11. LV and APM.
12. RCA.
13. LAD.
14. LCx.

Conducting system

Indications for examining the conducting system

1. History of asyncope.
2. History of arrhythmia.
3. Negative autopsy.

Sinoatrial node

• Sinoatrial (SA) node is at the lateral aspect of sulcus terminalis; lateral aspect of the superior vena cava and right atrium junction.
  • Cannot be identified grossly.
  • Artery of the SA (branch of RCA) may be a clue to where it lies.

Submitting the SA Node:

• Submit all of lateral sulcus terminalis -- serially section perpendicular to the sulcus terminalis, i.e. cuts are in the axis of the SVC (superior to inferior).

Notes: Gulino has a good description and good pictures.

SA node histology

The SA node is best identified by it location:

• The SA Node is superficial to cardiac muscle, i.e. distant to the RA relative to the cardiac muscle.
  • The SA nodal tissue abuts cardiac muscle.
• It sits around the sinoatrial node artery - which should be seen on its lumen if the section were taken properly.
• The SA node is deep to adipose tissue that covers that epicardial aspect of the heart.
• Nerve fibres (from the vagus nerve) are typically found between that adipose tissue and SA nodal tissue.

Histologic characteristics:

• Spindle cell morphology + wavy nucleus.
• Cytoplasms stains lighter with eosin than cardiac muscle.
• +/-Vacuoles.

Images:

• SA node - low mag. - vignetting (WC).
• SA node - low mag. (WC).
• SA node - high mag.(WC).

Atrioventricular node

Approach 1 (Peter method):

• Open the LVOT - if it hasn't been opened yet.
• Cut a section of that includes the right coronary cusp (of the aortic valve) and about 1.5 cm below it (this has the membranous septum and the superior muscular septum).
  • This section should then be serially sectioned in the axis of the VLOT.

Approach 2 (Virmani method):

1. View from right atrium: AV node is between the coronary sinus and membranous septum.
2. View from LVOT: Inferior to the posterior (non-coronary) cusp of the aortic valve.
   • One should cut a (coronal) section of that includes the posterior (non-coronary) cusp and about 1.5 cm below it (this has the membranous septum and the superior muscular septum) -- see: Figure 1-15 in Virmani et al.
     • This section should then be serially sectioned in the axis of the VLOT.

Approach 3 (Location by triangle of Koch):

• Atrioventicular (AV) node is in the triangle of Koch.

Triangle of Koch according to Virmani is the floor of the RA and:

• Tendon of Todaro = "superior".
• Tricuspid valve annulus = "inferior".
• Coronary sinus = "posterior".

Images:

• Triangle of Koch (ctsnet.org).
• Triangle of Koch (ctsnet.org).
• Triangle of Koch (ipej.org) from a paper by Macedo et al.

Tamponade

• Tamponade is a clinical diagnosis (classically: elevated JVP, low BP). It cannot be made at autopsy.

The pathologist (like radiologists) can say...

• Pericardial effusion.
  • Hemopericardium.

Image: Pericardial effusion - CT scan (wikipedia.org).

Myocardial infarction

Clinical

• Usually diagnosed clinically - with blood work (troponin, CK-MB) or EKG.
• MI may be precipitated by cocaine use... and further exacerbated by treatment with a beta-blocker.

Classic symptoms:

• Chest pain (with radiation down the arms).
• Nausea & vomiting.
• Diaphoresis.

Post-MI:

• Dressler's syndrome AKA postmyocardial infarction syndrome; pericarditis post-myocardial infarction +/- pericardial effusion (clinically tamponade).

Enzymatic tests:

• CK: peaks at day 1, resolves after 2-3 days.
• AST: peaks close to day 2, resolves after 4-5 days.
• LDH: peaks day 2, resolves after ~6 days.

Pathologic

Microscopic

Sequence:

• 1-3 hours - Wavy (myocardial) fibers
• 4-12 hours - Coagulative necrosis & loss of cross striations, contraction bands, edema, hemorrhage, PMN infiltrate.
• 18-24 hours - Coagulative necrosis, pyknosis of nuclei, and marginal contraction bands.
• 1-3 days - Loss of nuclei (karyolysis), loss of striations, abundant PMNs.
• 3-7 days - Macrophage and mononuclear infiltration, fibrovascular response.
• 10-21 days - Fibrovascular response, prominent granulation tissue.
• 6 weeks - Fibrosis.

Gross

Sequence:

• 18-24 hours - myocardial pallor.
• 1-3 days - pallor, moderate hyperemia (redness due to congestion with blood).
• 3-7 days - yellow lesion with hyperemic border.
• 10-21 days - maximally yellow.
• 6 weeks - white (fibrosis).

Coronary artery atherosclerosis

• Greater than 75% (diameter) stenosis - considered significant.

Stenosis definition (as per NASCET):
$percentstenosis=(1-(minimal\ diameter)/(poststenotic\ diameter))x100\%.$

With a bit of allegbra one can show:
$A_{x}=x^{2}A_{o}$
Where:

• x = 1 - (percent diameter reduction/100).
• A_o = the initial area.
• A_x = the area with diameter x.

If one applies the above equation:

• A 50% diameter reduction results in a 75% area reduction.
• A 75% diameter reduction results in a 93.75% area reduction.
• A 90% diameter reduction results in a 99% area reduction.

Abnormal hearts

Dilated pattern DDx:

• Hypertensive heart disease.
• Hypertrophic cardiomyopathy.
• Amyloidosis.

Cardiomyopathy

Main article: Cardiomyopathy

In the land of cardiology... there is a thing called cardiomyopathy.

Congenital heart disease

Main article: Congenital heart disease

Congential heart disease... a domain of paediatric cardiac surgery and occasionally adult cardiac surgery.

Tumours

Main article: Tumours of the heart

These are rare buggers.

Valvular disease

Main article: Valvular heart disease

This is the domain of cardiac surgery... only seen in hospitals with cardiac surgery.

Endocarditis

See Valvular heart disease.

Shunts

Most shunts are a consequence of congenital heart disease, which is dealt with in the congenital heart disease article. They are only listed here briefly and grouped into left-to-right and right-to-left.

Left-to-right

Mnemonic the Ds:

• ASD = atrial septal defect.
• VSD = ventricular septal defect.
• AVSD = atrioventricular defect.
• PDA = patent ductus arteriosus.

Note: The word Left has four letters and there are four L->R shunts.

Right-to-left

Mnemonic 5 Ts:

• Tetralogy of Fallot (TOF),
• Transposition of great arteries,
• Truncus arteriosus,
• Tricuspid valve atresia,
• Total anomalous pulmonary venous return.

Clinical: TOF is the classic cause of "blue babies".

Cardiac sarcoidosis

Main article: Sarcoidosis

General

• Can be in insolation or part of systemic sarcoidosis.
• May mimic hypertrophic cardiomyopathy clinically.
• Clinical: associated with heart block.

Gross

• Ventricular septum base - most common site of involvement.

Distribution by autopsy findings:

• Septum - 31.5%.
• Posterior LV - 24.6%.
• Anterior LV - 18.0%.
• RV - 17.9%.
  • RV involvement may lead to confusion with arrhythmogenic right ventricular cardiomyopathy (ARVC).
• Lateral LV - 14.1%.

Notes:

• Advanced lesions are fibrotic and may mimic old infarcts (grossly) due to coronary artery atherosclerosis.

Histology

Features:

• Non-caseating granulomas.
• Subepicardial predominance.
• +/-Fibrosis - old lesions are fibrotic.

Negatives:

• Significant number of eosinophils.
• Myocyte necrosis.

Notes:

• Myocyte necrosis and eosinophils are features of granulomatous myocarditis.

Myocarditis

Work-up

• Requires 10 sections to exclude; sections should include RV and LV.
  • It is often missed with five.

Classification

• Eosinophilic - hypersensitivity myocarditis - most common.
• Lymphocytic - viral, autoimmune.
• Granulomatous.
• Neutrophilic.
• Reperfusion (associated with myocardial infarction).

Granulomatous myocarditis

General

• AKA giant cell myocarditis.

Histology

Features:

• Granulomas.
• Myocyte necrosis.
• Eosinophils.

Note:

• Eosinophils and myocyte necrosis differentiate this entity from cardiac sarcoidosis.

Cardiac amyloidosis

Main article: amyloidosis

General

• Amyloid in the heart.
• Rare.

Histology

Features (H&E stain):

• Acellular fluffy pink material.

Special stains:

• Congo red stain - red (normal light), apple-green in polarized light.
• Thioflavin-T stain

Images (amyloidosis cardiac):

• Cardiac amyloidosis - H&E (WC).

Images (amyloidosis - non-cardiac):

• Amyloid in small bowel - congo red stain (WC).
• Amyloid in small bowel - H&E (WC).

Notes:

• ABCs of pink on H&E = amyloid, blood (fibrin), collagen, smooth muscle.

Cocaine toxicity

General

• Anatomical pathology findings at autopsy are uncommon (most common situation) or non-specific (atherosclerosis +/- acute thrombosis).
• Toxicity mechanisms:
  • Direct effects of norepinephrine on myocytes
  • Vasospasm leading to myocardial ischemia.

Gross

Features:

• +/-Atherosclerosis out of keeping with age.
• +/-Large areas of confluent necrosis.
• +/-Fibrosis.

Microscopic

Features:

• +/-Large areas of confluent necrosis.
• +/-Contraction band necrosis.
• +/-Fibrosis.
• +/-Myocarditis (usu. eosinophilic).

See also

• Basics.
• Cardiovascular pathology.
• Forensic pathology.
• Medical lung disease.
• Pulmonary hypertension.