107. Pericardium

Question 1

2 layers of the pericardium

Answer 1

1. outter/ fibrous2. inner/serous—made up of parietal (fused with fibrous layer) and visceral (adhered tightly to epicardium) layersparietal layer is collagenousvisceral layer is elastic

Question 2

what is the blood supply to the pericardium

Answer 2

paired pericardial and pericardiophrenic branches of the internal thoracic artery (branch from L subclavian artery)

Question 3

functions of pericardium

Answer 3

1. maintains hearts position (sternopericardiac ligament)2. restrains cardiac filling (noncompliant, pressure increase rapidly)3. protects the heart (ie. rupture, spread of infection or neoplasia)4. provides gliding surface (1-15ml fluid, ultra filtrate of serum, 25% colloid P of serum)

Question 4

chronic vs acute pericardial effusion

Answer 4

acute fluid: noncompliant pericardium cannot compensate well chronic fluid: some stretch in pericardium is seen and pericardium can accommodate a larger volume of fluid before pressure increases drastically (up to a point)

Question 5

consequence of increase pericardial pressure

Answer 5

increases diastolic pressure (reduces stroke volume)equilibrates with the right side of the heart first (r sided cardiac tamponade)decreases CO and compensatory mechanisms (SNS, RAAS) take over to incr HR and incr systemic vascular resistance in attempts to maintain blood pressure and vascular volumeANP (released with stretch of atria) cannot be released bc of tamponade, no inhibition of RAAS–> continued incr in portal and CV pressures eventually tamponade puts pressures on coronary arteries which leads too poor myocardial perfusion and eventually affecting contractility

Question 6

define pulsus paradoxus

Answer 6

variation in arterial pressures with respirationinspiration: decline in blood pressureexhalation: increase during exhalationvariation is often > 10 mm HgNOT pathognomonic for tamponade (can include obstructive lung disease, restrictive cardiomyopathy, hypovolemic shock)

Question 7

pericardial rupture

Answer 7

uncommonly associated with clinical signs UNLESS pericardium contracts around the herniated heart and kink cd vena cavaleading to Budd Chiari signs (ascites, hepatomegaly, caval syndrome)diagnose with caval angiographytx: right lateral thoracotomy, transection, +/- angioplasty

Question 8

pericardial effusion

Answer 8

–transudate (hypoalb, CHF, PPDH)–exudate (infectious Coccidiodes, noninfectious FIP)–hemorrhagic (idiopathic #1, neoplasia #2, trauma, rodenticide)

Question 9

tumors causing hemorrhagic effusions

Answer 9

1. HSA2. chemodectomas (brachycephalic dogs)3. mesothelioma

Question 10

T/Fcytology of pericardial fluid is NOT reliable for determining the presence of neoplasia

Answer 10

TRUEcytology of pericardial fluid is NOT reliable for determining the presence of neoplasiaand reactive mesothelial cells do NOT correlate with mesothelioma

Question 11

what is electrical alternans

Answer 11

EKG abNbeat to beat variation in shape and size of QRS and ST segmentsstrongly suggestive of pericardial effusion

Question 12

thoracic radiograph findings suggestive of pericardial effusion

Answer 12

—globoid heart shape—cardiac silhouette loses its angles and waists–caudal vena cava widens–pulmonary vascular underperfusion/undersized—+/- tracheal deviation if masses present —+/- ST/fluid superimposition if masses and/or pleural fluid presentCote et al JAVMA 2013 concluded radiographic signs of pericardial effusion were not SN in diagnosing

Question 13

location of pericardiocenesis

Answer 13

RIGHT 5-6th IC space in order to avoid coronary arteriesmonitor with EKG

Question 14

mechanism behind pericardiectomy for tx of idiopathic pericardial effusion

Answer 14

1. decreases surface area of pericardium, decreases fluid production2. increases surface area for absorption by allowing fluid into pleural cavity

Question 15

methods of pericardiectomy/pericardiotomy

Answer 15

1. SUBTOTAL–median sternotomy, right lateral thoracotomy, transdiaphragmatic subxiphoid open approach OR MI right lateral or transdiaphragmatic subxiphoid thorascopic approachperformed ventral to phrenic nerves2. Complete—accomplished with median sternotomy to visualize both phrenic nerves3. WINDOW—right lateral or subxiphoid thorascopic4. percutaneous balloon pericardiotomy—fluoroscopy guided

Question 16

sufficient size of pericardial window in a large breed dog

Answer 16

3 cm x 3 cm without risking herniation

Question 17

most common complication in dogs undergoing percardiectomy

Answer 17

pleural effusion—thoracostomy tubepoor px sign if pleural effusion develops > 30 days post op

Question 18

outcome of idiopathic pleural effusion treated with subtotal pericardiectomy

Answer 18

EXCELLENT unless other conditions (cardiomyopathy, neoplasia unrecognized at previous imaging/surgery)72% survive long term12% died perioperatively

Question 19

T/FCVP do NOT decrease with inspiration in dogs with constrictive pericarditis

Answer 19

true bc negative intrathoracic pressure inspiration is not transmitted to the cardiac chambers in dogs with constrictive pericarditisKussmaul sign

Question 20

what is Kussmaul sign

Answer 20

persistent increase in jugular venous pressure during inspiration (pressure does not decrease as it normally would)

Question 21

approach for epicardial pacemaker implantation

Answer 21

midline celiotomy and transdiaphragmatic approach to thoraxopen pericardiumscrew in electrode into left ventricular apex (usually 2.5 turns) ALT suture in leads to epicardium with non absorbable suturebring lead wire into abdominal cavity, connect to pulse generator and place in pocket created btwn transverses abdominis and internal abdominal oblique muscles

Question 22

most common pacing mode in small animals

Answer 22

VVIventricular sensingventricular pacinginhibited mode(pacemaker is intended to pace the cardiac ventricles but it will sense naturally occurring ventricular impulses and will inhibit its own output when they occur–prevent competitive rhythms)paced at 70-110 bpm with 4-5 VEKG has stimulus artifact prior to paced QRS-T complex (failure to pace will show as artifact without QRS-T complex or patient will have lack of an arterial pulse; failure to sense will show up as competitive rhythms–risk tachycardia/Vfib)

Question 23

routes of placemaker placement

Answer 23

1. epicardial—open surgical approach with screw in or suture in leads2. endocardial—transvenous MI approach through jugular vein placed on endocardium; less invasive but higher incidence of catheter dislodgment