12-06-2066Autopsy dissection ofthe Heart and theSpinal cord Dr. Rijen Shrestha M.D. Resident Dept. of Forensic Medicine
references: ludwig for heart anatomy books by foreign authors(no names included) spinal and scrotum -gresham and turner +ludwigs dissection techniques recommendations given after presentation: short pause between change of slides, more details on layers of scrotum and heading as dissection of spinal cord and not vertebral column.. heart dissection can be tried or practiced by u..but sudnt forget the names..in regular autopsy.. THign learnt: myocardium dissection sud not be done like we do in there..whole myocardium sud be subjected to rule out artifects produced by formaldehyde to middle layer of myocardium.
Dissection of heart Removal of heart:-chest plateHeart -thoracic bloc: pericardial adhesion, previous h/o open heart surgery, pericarditis, congenital cardiac disease, esophageal/pulmonary carcinoma, aortic dissection , injuries to heart (tamponade).Heart- removed separately acquired diseases , no adhesions or injuries to heart.
Color of myocardium: Gray : old infarct Pale : anemic Mottled/hemorrhagic spots: acute infarct/ruptureShape: Conical : normal Irregular/globoid : verntricular aneurysms, ventricular thromboembolism, 1 or more chamber irregular in shape(DCM)
Evaluation of coronaries: -Before any forms of cardiac dissection is applied, coronaries should be inspected for calcification and tortuosity. -Subjects younger than 30yrs or where cause of death is non cardiac: coronaries may be opened longitudinally -Otherwise, transverse section : 3.5-5mm . -Calcified vessels are stripped off and decalcified.
Grading of coronary obstruction:-Mild :grade I: > 25% narrowing (cut off point)-severe : to 70%, critical stenosis : >90% (grade IV) -Depending on number of vessel involved:vessel 1,2,3..if LAD is involved..vessel4. Ex:grade 4-critical- vessel4 = >90%, critical stenosisinvolving all 4 major coronaries.
Cardiac dissection methods:1. Inflow-outflow method2. Short-axis method Useful for3. Four chamber method demonstrating cardiac pathology4. Long axis method Anatomic 5.Base of heart method teaching and museum 6.Window method specimen 7.Unrolling method demonstrationsConsiderable Mutilation 8.Partition method. / preparations.of the heart
1. Inflow-outflow method:Right: -Using scissors, initial cut is made from IVC to right atrial appendage sparing SVC and SA node. -Right ventricle opened with knife along 1cm parallel to the posterior ventricular septum -Outflow tract :1cm parallel to anterior ventricular septumLeft: -Left atrium-between R and L pulmonary veins -Left atrial appendage checked for mural thrombus. -Inflow tract: left ventricle opened along its inferolateral border. -Outflow tract :to avoid damage to mitral valve, 1cm parallel to anterior ventricular septal groove.
2. Short Axis dissection: -Method of choice :slices expose largest surface area of myocardium. -Diaphragmatic aspect kept over paper towel to prevent slippage. - 1.0-1.5cm thick cuts parallel to atrio- ventricular groove with long knife. -One firm slice -Each slice viewed from apex to base.
3. Four chamber method: -long knife, begin at apex of the heart. -cut extended through acute margin of right ventricle, obtuse margin of left ventricle and ventricular septum. -cutting extended through mitral and tricuspid valve through atria. -divides heart into 2 pieces each having all 4 chambers. -Upper half can be opened using inflow-outflow technique.
4. Long axis method: -3 straight pins are used to demarcate. -First pin : apex, 2nd pin : right aortic sinus (just adjacent to right coronary sinus) 3rd pin: near mitral valve annulus (between 2 pulmonary veins openings). -Heart is cut along this plane from apex to base or vice versa using knife and scissors passing through both mitral and aortic valves.
5.Base of the heart method: -Displays all the valves -Ideal for demonstrating anatomical relations of the valves and adjacent coronaries.6. Window method : -Perfusion fixed, window of various sizes removed with scalpel and sent for HP study. -Small windows, enlarged depending on the size of the lesions. -Useful for cardiac museum specimen.
7.Unrolling method: -Causes considerable mutilation of the heart, only done in research studies.8. Partition method: -Coronaries and epicardial fats are stripped off -Ventricles separated from IV septum, atria removed. -All weighed separately. -Mutilation.
Dissection of cardiac conduction system: -procedure of no practical diagnostic value - mentioned at instances in literatures but in practice such examination is not performed.Quantitative measurements of the heart: -Weight -Wall thickness -Valve size -Amount of pericardial fluidQualitative analysis of the heart: -Cardiac valve patency - Embolism
Weight of the heart: “Total heart weight is most reliable single measurement at autopsy for correlation with cardiac disease states.”-Reiner .L., Gross examination of heart, Pathology of heart and great vessels, 3rdedition, IL, pp1111-1149. Other described measurements like linear external dimension, surface area and volume of entire myocardium are less useful.-great vessels are trimmed to about 2cms in length.-PM clots are removed.-weights recorded (+/- 5gms adult; =/- 0.1gms infants)-fixation alters the weight by 5-10%-heart weight proportional to body weight rather than age, gender and body size.
Thickness of walls of heart: -usually measured at the level of mitral valve; but since the wall is thin towards apex and thick towards base; -MOST reliable average measurement is found at level of papillary muscles. -ventricular septum and right ventricle should also be measured at the same level. -Trabeculations and papillary muscles should be excluded. -Fixation increases the size by 10%.Confusions: -physiological hypertrophy - 25% in athletes. -decomposition vs. dilatation -postmortem > 24hrs, RM passes –natural dilatation vs.
Cardiac valve patency/Size: ◦ Regurgitation can be accessed to some extent by filling chambers with water to check for retrograde flow through intact valve. ◦ Stenosis and valve size is best evaluated by measuring effective orifice size by a calibrated cone (but not annular size). ◦ Thickness and area of valve increase with age and is higher in females than males of same body size.
Air embolism :-first coronaries, to check for systemic air embolism.-all chambers to be perforated, RV-LV-RA- LA.
Anterior Approach: -first cut is made across uppermost part of T1 or T2. -head is dropped back, wooden block under mid back. -either side of thoracic spine up to length of 15cms. -angle of blade changed and adjusted according to the type of vertebra. -muscles removed and vertebra(L1-L4) cut in similar pattern like thoracic vertebra. Sacrum and L5 is removed together. -Carotids are pushed sideways and cervical vertebrae removed till c2 similarly.
Advantages: -prevents leakage after embalming. -less mutilation visible. -course of peripheral nerves for any length in contiguity from spinal cord can be accessed.Disadvantages: -difficult approach to proximal cervical vertebrae -conditions like myelomeningocele, and occipital encephalocele cannot be demonstrated. -Flexion extension injuries to back of the neck or other injuries along the posterior vertebral column cannot be demonstrated.
Posterior approach: -Body prone, wooden blocks under both shoulders. -Head rotated forward, flexed. -Midline incision over spinous processes, muscles are resected. -Parallel saw-cuts through vertebral laminae -Cauda equina divided and lifted up by Spencer Wells forceps. -Not to twist or bend the spinal cord.
Advantages: -Pathological conditions like myelomeningocele, occipital encephalocele can be demonstrated.- -dissection can be limited up to the desired level and stopped.- -both anterior and posterior aspect of vertebra can be accessed.Disadvantages: -course of peripheral nerves cannot be pursued along its contiguity. -Embalming leakage -Cosmetic disadvantage.
Combinedapproach:- For complete removal of meningocele, myelomeningocele or other midline fusion defect-Body is turned back and incision is made around the desired area then continued anteriorly.