Myocardial preservation during anoxic arrest. Experimental model ventricular fibrillation

The outcome after aortic valve-sparing (David) operation in 179 patients: a single-centre experience

OBJECTIVES

The David aortic valve-sparing reimplantation (AVr-D) operation is increasingly being used in patients with aortic root aneurysmal disease and pliable aortic cusps. The objective of this study was to assess our early and medium-term outcomes with the AVr-D operation.

METHODS

Between 2003 and 2011, a total of 179 patients underwent AVr-D procedures. The mean patient age was 49.7 ± 15.1 years, and 23.5% (n = 42) were females. Marfan syndrome was present in 17.3% of patients (n = 31), and acute Type A aortic dissection in 15.6% (n = 28). Clinical follow-up was 100% complete and was 1.8 ± 1.6 years (0 days to 7.5 years) long. Echocardiographic follow-up was performed 2.2 ± 1.5 years (0 days to 7.5 years) postoperatively and was 77% complete.

RESULTS

Early mortality was 1.1% (n = 2), with both deaths occurring in patients with Type A dissection. Pre-discharge echocardiography revealed no patients with >2+ aortic insufficiency (AI), 19.6% of patients (n = 34) with 1+ or 2+ AI and 80.4% of patients (n = 145) with trace or no AI. Left ventricular end-diastolic diameters decreased significantly from 5.6 ± 0.9 to 5.1 ± 0.8 cm early postoperatively (P < 0.01). Transvalvular maximum gradients were similar before discharge and at last follow-up (10.6 ± 5.4 vs. 10.0 ± 8.2 mmHg, P = 0.4). AI grade increased significantly over time (0.3 ± 0.4 before discharge vs. 0.5 ± 0.6 at follow-up, P = 0.01), but remained less than moderate in 93.6% of patients. Four patients required aortic valve re-replacement during follow-up, two due to early endocarditis and two due to non-coronary leaflet prolapse in Marfan patients. Five-year freedom from aortic valve reoperation was 95.9 ± 2.0%.

CONCLUSIONS

AVr-D is associated with a low mortality and morbidity rate, even in patients with Type A aortic dissection. Although a slightly higher rate of recurrent AI may be present in patients with Marfan syndrome, freedom from recurrent AI and reoperation remains excellent during medium-term follow-up. The David operation should be considered the gold standard for patients with proximal aortic root pathology (aneurysm or dissection) and pliable aortic cusps.

Intramyocardial temperature following various cooling procedures

In 12 dogs on cardiopulmonary bypass, the intramyocardial temperatures in the anterior and the posterior wall of the left ventricle and in the septum were measured with microthermoelectrodes when different cooling procedures were used during 60 min of anoxic cardiac arrest. External cooling with 4 degrees C glucose (5.5%) solution dripping into the pericardial sac did not lower the temperature in the septum or in the posterior wall. Packing the heart in slushed ice after injection of the same glucose solution into the coronary tree reduced the septum and posterior wall temperature to around 30 degrees C. This cooling procedure, in combination with general moderate hypothermia, lowered the temperature to about 20 degrees C in these parts of the heart. Only when combined with general hypothermia did local cooling achieve low temperatures in all regions of the myocardium.

Myocardial preservation during anoxic arrest. Premedication with propranolol, verapamil or methylprednisolone

Anoxic cardiac arrest was studied for one hour in five groups of dogs. Groups I-III were given methylprednisolone (30 mg/kg b.w.) before aortic cross-clamping. Normothermia was used with electrically induced ventricular fibrillation in group I, and without such fibrillation in group II, while group III was studied in local hypothermia. Propranolol (10 micrograms/kg) was given to group IV and verapamil (0.2 mg/kg) to group V before the anoxic arrest in local hypothermia. Judged from the ability of the heart to take over the circulation after anoxic arrest, local cooling preceded by propranolol or verapamil gave working performance comparable with the pre-arrest values. In the cooled, steroid-pretreated hearts the work capacity was depressed to the same degree as in locally cooled hearts without steroid premedication. Methylprednisolone prevented ischemic contracture during normothermic arrest with induced fibrillation, but not in the absence of such fibrillation. As adjuvant to local cooling, pretreatment with metabolism-reducing drugs is favorable for cardiac performance after arrest. Steroid premedication should be considered when normothermic arrest with electrically induced ventricular fibrillation is planned.

Myocardial preservation during anoxic arrest. Chemical cardioplegia

Two types of cardioplegic solution--the potassium arrest and the Bretschneider solution, both at 4 degrees C--were compared with regard to protective effect against ischemic damage during 60 min of anoxic cardiac arrest in the dog heart. Both solutions provided equally good protection, which was superior to that given by hypothermia alone.