107. Pericardium Flashcards
2 layers of the pericardium
- 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
what is the blood supply to the pericardium
paired pericardial and pericardiophrenic branches of the internal thoracic artery (branch from L subclavian artery)
functions of pericardium
- 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)
chronic vs acute pericardial effusion
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)
consequence of increase pericardial pressure
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
define pulsus paradoxus
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)
pericardial rupture
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
pericardial effusion
–transudate (hypoalb, CHF, PPDH)–exudate (infectious Coccidiodes, noninfectious FIP)–hemorrhagic (idiopathic #1, neoplasia #2, trauma, rodenticide)
tumors causing hemorrhagic effusions
- HSA2. chemodectomas (brachycephalic dogs)3. mesothelioma
T/Fcytology of pericardial fluid is NOT reliable for determining the presence of neoplasia
TRUEcytology of pericardial fluid is NOT reliable for determining the presence of neoplasiaand reactive mesothelial cells do NOT correlate with mesothelioma
what is electrical alternans
EKG abNbeat to beat variation in shape and size of QRS and ST segmentsstrongly suggestive of pericardial effusion
thoracic radiograph findings suggestive of pericardial effusion
—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
location of pericardiocenesis
RIGHT 5-6th IC space in order to avoid coronary arteriesmonitor with EKG
mechanism behind pericardiectomy for tx of idiopathic pericardial effusion
- decreases surface area of pericardium, decreases fluid production2. increases surface area for absorption by allowing fluid into pleural cavity
methods of pericardiectomy/pericardiotomy
- 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
sufficient size of pericardial window in a large breed dog
3 cm x 3 cm without risking herniation
most common complication in dogs undergoing percardiectomy
pleural effusion—thoracostomy tubepoor px sign if pleural effusion develops > 30 days post op
outcome of idiopathic pleural effusion treated with subtotal pericardiectomy
EXCELLENT unless other conditions (cardiomyopathy, neoplasia unrecognized at previous imaging/surgery)72% survive long term12% died perioperatively
T/FCVP do NOT decrease with inspiration in dogs with constrictive pericarditis
true bc negative intrathoracic pressure inspiration is not transmitted to the cardiac chambers in dogs with constrictive pericarditisKussmaul sign
what is Kussmaul sign
persistent increase in jugular venous pressure during inspiration (pressure does not decrease as it normally would)
approach for epicardial pacemaker implantation
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
most common pacing mode in small animals
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)
routes of placemaker placement
- 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
