Chapter 6

Cardiovascular Surgery

   

 6.1 Review

-- Please review:

Surgical Anatomy

Functional Physiology

  • --Systemic Arterial BP
  • --Adequate Tissue Perfusion
  • --Venous BP
  • --Also review:
  • Systolic function
  • --Preload
  • --Afterload
  • --Contractility
  • Heart Rate

Diastolic Function

  • --Factors affecting the above
  • --Further Review:

Heart Failure and its Classification(HF)

  • --1. Forward versus Backward
  • --2. Acute versus Chronic
  • --3. Sec. to Myocardial Failure
  • --4. Sec. to Left to Right Shunts
  • --5. Sec. to Severe Regurgitation
  • --6. Sec. to Pressure Overloads

EKG: Technique and Interpretation

Radiography of CVs: Techniques(Survey/Contrast)

Selective Catheterization, Echocardiography,

Phonocardiography, and INTERPRETATION 

6.2 PHYSICAL EXAMINATION OF THE CARDIOVASCULAR SYSTEM

Minimum Data Base should include:

6.2.1 Signalment

  • Primary Complaint
  • Clinical History
  • Physical Exam
  • Clinical Lab. Profile
  • EKG
  • Thoracic Radiography
  • Other Ancillary Tests:
  • Phonocardiography
  • Echocardiography
  • Cardiac Catheterization
    • --Selective/Non-selective angiography
    • --Pressure Recording & Differentials
    • --Cardiac Output measurement
    • --Oximetery

6.2.1 SIGNALMENT:

AGE: 

Young:

Congenital

Old:

Acquired

BREED 

Poodle

PDA

E. Bulldog:

Pulmonic Stenosis

Boxer:

Neoplasia

Newfoundland:

Sybaritic Stenosis

Great Dane:

Cardiomyopathy

SEX: Less significant

Females:

PDA

Male Cats:

Cardiomyopathy

Male Cocker Spaniels:

Valvular Insuff

6.2.2 HISTORY:

  • Should include:
  • Current Complaint
  • Onset and Duration
  • Pertinent Past Disorders
  • Environmental details Vaccinations
  • Hereditary/Family History
  • Medications Currently on and Response
  • Attitude and Behavior
  • Activity, Excerise tolerance
  • Appetite: Food type & water consup.
  • Elimination habits
  • Seizures or fainting episodes
  • Coughing, Vomiting Sneezing
  • Ambulation, Dyspnea
  • Weight fluctuations
  • Edema/Swelling
  • Poor growth or Performance
  • Try to differentiate between Cardiac and Pulmonary Problems

6.2.3 PHYSICAL EXAMINATION

  • Evaluate the entire animal
  • Identify all the problems
  • Cardiovascular problems need further exploration and delineation from pulmonary problems

6.2.4 OBSERVATION/INSPECTION:

Starts from waiting room

  • -Abn. in gait, attitude, appearance, posture.
  • -Refusal to lie down, abducted elbows, flared nostrils open mouth breathing.
  • -Rate, rhythm and depth of respiration
  • -Dyspnea-inspiratory/expiratory?

obstructive/restrictive

  • -Coughing-its character, sneezing, or wheezing
  • -Ascities, edema-its location
  • -CRT & Color of m.m.& comparison
  • -Jugular distention

6.2.5 PALPATION:

Evaluate

  • -Shifting of Point of maximum intensity(PMI) of the heart beat, cardiac thrill
  • -Abd. palpation and contour, fluid waves?
    • Abnormalities in femoral pulses-in rate.
    • rhythm, intensity. Compare to HR.

6.2.6 PERCUSSION:

  • -Cardiomegaly,hyperresonance.fluid waves

6.2.7 AUSCULTATION:

All areas of the heart and lungs are to be evaluated. Evaluated heart over the pulmonic, aortic, mitral and tricuspid area: 

Area

Canine Location

Feline Location

Pulmonic

L 2-4; ICS just above sternum

L 2-3; ICS; junction. upper & mid. 3rd

Aortic

L4: ICS above Costo-chond.

L 2-3; ICS dorsal Junc. to pulm. area

Mitral L5;ICS at CCJ

L5-6;ICS lower

1/4 of chest

Tricuspid

R3-5;ICS;CCJ

R4-5;ICS;at lower1/4 of chest

6.3 SELECTED CARDIOVASCULAR ANOMALIES & THEIR SURGICAL MANAGEMENT

6.3.1 PATENT DUCTUS ARTERIOSUS:

The most common congenital heart disease. Has a polygenic mode of inheritance.

6.3.1.1 ETIOPATHOGENESIS:

  • -Failure of the 6th aortic arch to achieve a functional closure in the immediateprenatal period, resulting in a L-R shunt.
  • -Continuous shunting of blood from aorta to main pulm. artery, results in
    • a) volume overload
    • b) subsequent dilation of the left side of the heart,
    • c) resultant mitral insuff. thereby contributing to pulm. venous congestion. pulm. edema and pronounced dyspnea, tachypnea, coughing and other resp. signs
  • -Increased shunting through pulm. vasculature may cause initial fibrosis and muscular hypertrophy resulting into increased pulm. resistance and hypertension thereby causing reversed or bidirectional shunting of blood through the ductus
  • -In reversed PDA unoxygenated blood is mixed with oxygenated aortic blood and shunted to the caudal areas of the body resulting in differential cyanosis, chronic renal bypoxemia, increased erythropoietin levels and polycythemia.

6.3.1.2 CLINICAL PRESENTATION AND SYMPTOMS:

BP:

Poodles, Spaniels, G. Shep., Yorkies, Pomeranians, Collies, Shelties.

SIGNS:

  • -Variable. None in the beginning
  • -Exercise intolerance, tachypnea, cough and other progressive resp. problems due to L-sided backward H. failure.
  • -Continuous machinery murmur in the lower L-3. I/C space which may radiate to R base. Presence of pericardial thrill, holosystolic S2 murmur, hyperkinetic pulse and pink m.m. are evident unless reverse shunting supervenes where differential cyanosis predominates.
  • -Death occurs at an early age in untreated animals.

DIAGNOSIS:

  • -BP, history & PE, CBC, Blood gases
  • -EKG: LVH with wide P. Very tall R & deep Q waves and S-T segment deviation.
  • -Echocardiography. LH enlargement. Dilation of pulm. trunk and ductus image is sometimes visible.
  • -Radiography: LHF with L atrial and L auri, enlargement, pulm. over circulation and edema. Aortic bulge
  • -Contrast angiocardiography: L-R shunting of opacified blood through the ductus. Mitral or pulm. Valvular insuff.

Cardiact catheterization: Higher blood oxygen levels in pulm. artery Vs. R vent. and increased pressure reading in various cardiac chambers.

TREATMENT:

  • -Surgical ligation of L-R shunt as early as possible (2-4 M)
  • -Uncomplicated cases, on surgical correction, are expected to have a normal life span.
  • -Complicated cases of L-R PDA with L sided HF need additional medical management.

PROGNOSIS:

  • -Excellent to good in young and uncomplicated cases.
  • -Without surgery 60% die in first year post-diagnosis.

SURGICAL TECHNIQUE:

  • -L-4 I/C thoracotomy
  • -Reflect the lungs and identify the ductus coarsing/communicating between the aorta and pulm. art.,
  • -Incise mediastinal pleura over aorta just dorsal to vagus.

Dissect it dorsally over aorta and ventrally over the pulm. art., The ventral mediastinal flap along with vagus may be tagged with a 3/0 stay suture and retracted

  • -Dissect aorta loose from the surrounding areolar tissue along its dorsal and R-medial borders.
  • -A R- angled Mixter forceps or a Halstead mosquito forceps are passed medially around the ascending aorta proximal to PDA and a 2/0-0 non-absorbale suture (e.g. silk) of 40-50 cm length is caught in the forceps at its midpoint and withdrawn so as to rest it around the medial aspect of the aorta.
  • -The same forceps are passed in a similar manner around the descending aorta caudal to the PDA. The free ends of the suture are caught in and withdrawn by the forceps thereby seating the suture loop on the R-side of PDA.
  • -The loop is divided to form two free strands. One strand is tied so as to ligate the PDA as close to the aorta as possible.

Next the 2nd strand is tied to ligate the pDA again close to the pulm..art.,

  • -Routine thoracotomy closure. Maintain negative pleural P.

POST-OPERATIVE PATIENT MONITORING:

  • -Repeat radiographs & EKG before discharge.
  • -Monitor EKG every 6 M.

6.3.2 PERSISTENT RIGHT AORTIC ARCH

6.3.2.1 ETIOPATHOGENESIS:

  • -A developmental anomaly where aorta is formed by the R-4 aortic arch instead of the usual L-4.
  • -Results into the entrapment of esophagus and trachea in vascular ring comprised of aortic arch on the right, base of the heart ventrally, pulm. art. and ligamentum arteriosum on the left, and dorsal aorta dorsally.
  • -Results in regurgitation of food and sec. aspiration pneumonia.

6.3.2.2 CLINICAL PRESENTATION AND SYMPTOMS:

BP:

  • Doberman, Great Dane, Irish setter, Weimaraner.

SIGNS:

  • -Regurgitation after eating. Starts at weaning on a diet of solid or semi-solid food
  • -Thin, emaciated, malnourished animal with ravenous appetite.

DIAGNOSIS:

  • -Signalment & History, and survey thoracic radiograms.
  • -Barium swallow esophagram confirms distended esophagus cranial to the base of the heart.
  • -R/O other causes of mega-esophagus.

TREATMENT:

  • Surgical division of ligamentum arteriosum between two ligatures
  • Free esophagus from the surrounding mediastinal adhesions
  • Follow surgical procedure as (nearly) outlined in PDA 

POST-OPERATIVE MANAGEMENT:

Frequent feeding of semisolid or gruel consistency of feed at table-top level with animal standing on its hind legs.

6.3.3 PULMONIC STENOSIS

6.3.3.1 ETIOPATHOGENESIS:

  • -One of the most common congenital cardiac disorder with multifactorial etiology.
  • -Most cases are moderate to severe(grade 2) with subvalvular or valvular lesions.
  • -Resultant outflow (blood) obstruction causes Rt. ventricular concentric hypertrophy, decreased CO, syncope, CHF, and subsequent tricuspid regurgitation. Rt. atrial dilation, and increased potential for atrial arrhythmia.
  • -Turbulent blood produces both the murmur and the post stenotic dilatation of pulm. art.,
  • -Concentric ventricular hypertrophy may limit coronary blood flow resulting into myocardial infarction, arrhythmia and sudden death.

6.3.3.2 CLINICAL PRESENTATION AND SYMPTOMS:

BP:

  • Bengal, Fox terrier, English bulldog, Chihuahua, Samoyed, Schnauzer, Boxer. 

SIGNS:

  • -Asymptomatic to mild exercise intolerance to syncope to Rt-sided CHF i.e. jugular pulsation, hepatic enlargement, ascites etc.
  • -Systolic, crescendo-decrescendo murmur of varied intensity, IV/V to VI/VI, at L 2-3, I/C at heart base. It radiates up toward scapula and to Rt. chest at heart base.

6.3.3.3 EKG:

  • -Rt. axis deviation (120+), P-pulmonale, sT segment deviation, A-Fib.

6.3.3.4 RADIOGRAPHY:

  • -RV & Rt, atrial enlargement, Normal to hypoperfused lungs .Post stenotic dilatation on DV views

6.3.3.5 CARDIAC CATHETERIZATION:

  • -Pressures: Increased RV end diastolic and Rt. atrial
  • Pressure drop across pulm. valve area.
  • -Contrast angiography: Selective RV injection confirms the stenosis and post-stenotic dilatation. Nonselective? 

6.3.3.6 ECHOCARDIOGRAPHY:

  • -Concentric RV hypertrophy, thickened pulm. valves, post-stenotic dilatation.
  • -Doppler study demonstrates pressure gradients/ differentials

6.3.3.7 DIAGNOSIS:

  • -PE, BP, Signs & symptoms, EKG, Radiography, Pressure gradients, Echocardiography and Catheterizations etc.
  • -R/O: Atrial septal defects, dirofilarisis, tetralogy of Fallot, and aortic stenosis.

6.3.3.8 TREATMENT:

  • -Supravalvular stenosis repaired by a bypass conduit.
  • -Valvular or subvalvular stenosis by:
    • Inflow occlusion-pulm. arteriotomy in mature animals.
    • Patch graft technique for immature animals.
    • Bistoury or modified Brock procedure or Valve dilator
    • technique or Balloon valvoplasty.

6.3.3.9 INDICATIONS FOR SURGERY:

  • -Severe RV hypertrophy to syncope to CHF
  • -RV pressure or gradient of 100+ mm Hg. across the valve in mature animals.
  • -RV pressure of less than 70 mm and gradient of less than 50 mm Hg does not require surgery.

6.3.3.10 SURGERY:

Patch technique:

  • -Left 4, I/C thoracotomy (6, I/C in cat)
  • -Incise an elliptical pericardial graft 1.5 times wider than the diameter of pulm. artery, ventral to the pherenic nerve, and store in physiologic saline until needed
  • -A curved atraumatic needle with a 3/0 multifilament steel wire suture is inserted through the RV wall into the RV, up the pulm. (valves) outflow tract and out of the pulm. artery.
  • -Absorbable 3/0-4/0 purse-string sutures are (pre?) placed at the points of entrance and emergence of the needle to control hemorrhage.
  • -The wire is positioned over the RV and pre- harvested pericardial patch is sutured, with sutures placed 2 m m apart, from the pulmonary art. to the RV tenting it over and covering the outer limb of the wire suture. The wire ends emerge through a 2-3 mm gap at the lower ventricular edge of the graft where a horizontal mattress suture is placed through the patch and left untied.
  • -The outflow tract and valve are opened by withdrawing the wire with a sawing motion. The horizontal mattress suture is tied after pulling the wire suture through the gap.
  • -Routine closure of thoracotomy incision. 

6.3.4 AORTIC STENOSIS

6.3.4.1 ETIOPATHOGENESIS:

  • -Subvalvular aortic fibrosis is the most common congenital, autosomal dominant, defect of the large breed dogs.
  • -Resultant LV outflow obst. causes pressure overload leading to LV concentric hypertrophy, myocardial ischemia, ventricular arrhythmia and sudden death.
  • -Stroke volume drops due to impaired ventricle inflow and outflow accompanied by papillary M. and subendocardial fibrosis and mineralization.

6.3.4.2 CLINICAL PRESENTATION AND SYMPTOMS:

HISTORY:

  • -Dyspnea, exercise intolerance, syncope, collapse, sudden death.

BP:

  • -Newfoundland, German Shepherd, Boxer, Golden retriever, German short hair pointer, Rottweiler etc.

SIGNS:

  • -Crescendo-decrescendo systolic murmur, heard best at left base of the heart, radiating to thoracic inlet and neck along with weak femoral pulses and signs listed in history.
  • -Mitral insuff. secondary to LV outflow obstruction

6.3.4.3 EKG:

  • -L-axis deviation, LV hypertrophy (tall & wide qrs), ST segment deviation, tall T waves and disarrhythmia.

6.3.4.4 RADIOGRAPHY:

  • -LV enlargement, loss of caudal waist, cardiomegaly, post- stenotic dilatation, LH failure. 

6.3.4.5 CARDIAC CATHETERIZATION:

Pressures: -LV outflow tract pressure gradient of more than 70 mm (100-220 mm)Hg.

  • -Higher the gradient lesser the chances of survival.
  • -May be asymptomatic at less than 50 mm.

Contrast angiography: -Radiographs taken 6-8 sec post I/V injection will image the post stenotic dilatation.

6.3.4.6 ECHOCARDIOGRAPHY:

  • -helps visualize the obstructing band, ventricular and septal hypertrophy.
  • -Aortic valve is thickened, diminished in range of motion and may appear to flutter in systole.
  • -Doppler study may help detect turbulence and regurg. assoc. with concurrent mitral & aortic insuff.

6.3.4.7 DIAGNOSIS:

  • -BP, History, pE, EKG, Radiography, Chamber pressures & gradients, Echocardiography.
  • -R/O. Pulmonic stenosis, Septal defects.

6.3.4.8 TREATMENT:

  • -Beta adrenergic blocking agents.
  • -Limited success with surgery. Techniques advocated are:
  • Balloon angioplasty
    • -Valvular Dialator
    • -Bistoury technique
    • -LV-aortic conduit bypass

    VALVULAR DILATOR TECHNIQUE:

    • -L-5, I/C thoracotomy.
    • -Incise pericardium parallel to long axis of the heart starting the incision just below the pherenic nerve towards the apex.
    • -Place a purse-string suture (one and a half cm. in diameter) deep into the myocardium at the left ventricular apex using a 2/0 abs. suture.
    • -Make a stab incision about 1 cm long in the center of the purse-string suture and insert the valve dilator into the ventricle and carefully advance it till the tip of the dilator is palpated in the aorta.
    • -The dilator is progressively opened till it tears the subvalvular fibrous ring, whereupon it is removed and the purse-string suture is tightened.
    • -Thoracotomy is routinely closed.

6.3.5 FELINE AORTIC EMBOLISM

6.3.5.1 ETIOPATHOGENESIS:

  • -A wide spread but uncommon major arterial disease occurring secondary to underlying feline cardiomyopathy.
  • -The embolus may originate from atrial or ventricular chambers and lodges at aortic termination.
  • -Clot generates vasoactive substances which block collaterals.

6.3.5.2 CLINICAL PRESENTATION AND SYMPTOMS:

  • -Sudden onset of pain, posterior paresis/paralysis.
  • -Distress, shock, constant crying, absence of femoral pulse.
  • -Affected limb(s): cooler, swollen, ischemic, cyanotic foot-pads and nail-beds, spastic gastrocnemius muscle(s).
  • -Cardiac murmur or abn. heart sounds on auscultation.
  • -Hematology may show slight hemoconcentration
  • -Clinical chemistry is normal or has elevated muscle enzymes

6.3.5.3 EKG:

  • May show LV hypertrophy, arrhythmias, incomp. LBBB.

6.3.5.4 RADIOGRAPHY:

  • -Hyportrophic or dilated cardiomyopathy.
  • -Venous angiography demonstrates the aortic blockage.

6.3.5.5 DIAGNOSIS:

  • -History, PE, EKG, Radiography
  • -R/O: Traumatic injuries, spinal compression

6.3.5.6 TREATMENT:

  • -Surgical removal of the embolus with in the first 4-6 hrs. yields best results.

6.3.5.7 SURGERY:

  • -Atropine and thiopental induction, isoflurane maintenance.
  • -R/L fluids spiked with soda-bicarb. (1 ml/10ml)
  • -Dorsal recumbent position with lumbar elevation
  • -Caudal linea-alba incision
  • -Pack off intestine cranially and incise the parietal peritoneum to expose aorta and illacs.
  • -Apply a bulldog clamp/umbilical tape cranial to the embolus
  • -Heparinized the cat (1 mg/lb). Open the aorta over the embolus and remove the obstruction
  • -Temporarily slacken the clamps to flush out remaining tiny emboli
  • -Suture the aortotomy with 6./0-7/0 monofilament polypropylene in a simple continuous/interrupted fashion
  • -Confirm presence of femoral pulses(s) before abdominal closure

6.3.5.8 POSTOPERATIVE MANAGEMENT:

  • -Maintain a volume/osmotic diuresis
  • -Heparin therapy, @ 10-15 mg tid, to continue for next 48 hrs.
  • -Antibiotic Rx for 10-14 days
  • -Aspirin 75 mg every 72 hrs for long term RX.
  • -Manage primary cause of cardiomyopathy.