Pressure-induced left ventricular hypertrophy in canine model of aortic stenosis using nylon tie

The aim of this study was to develop an experimentally-induced canine model of left ventricular hypertrophy through banding of the ascending aorta using nylon ties. Seven clinically normal dogs free of cardiovascular disease were used. Nylon tie was used in banding the mid-ascending aorta. Clinical, radiographic and echocardiographic evaluations were done at 1.5, 3 and 6 months. Dogs were euthanized at 6 months for post mortem and histopathological evaluation. Clinically, dogs did not exhibit any signs of cardiovascular disease at 1.5 or 3 months, while at 6 months two dogs (28.6 %) exhibited mild weight loss, exercise intolerance and heart murmurs. Radiographic evaluation revealed significant increase in cardiac size only at 6 months based on measurement of the cardiothoracic area evaluation. Echocardiography revealed increased left ventricular wall thickness starting from 1.5 month, although this increase was statistically significant at 3 and 6 months (p > 0.05). Left ventricular hypertrophy was confirmed by post mortem examination. Histopathological sections of left ventricle in all dogs demonstrated myocyte hypertrophy and interstitial fibrosis. This model simulates the naturally occurring ventricular hypertrophy using a rapid and economic technique. Such models are required to understand pathogenesis of heart disease and to develop effective treatment strategy.

Ringer acetate versus ringer lactate cardioplegia: a comparative study in mitral valve surgery

Background: ringer lactate has long been used in many surgical procedures as one of the isotonic solutions. However, with the development of Ringer acetate, it becomes the crystalloidof cholce owing to its main metabolism in muscles unlike lactate which is mainly in liver, also it corrects acidosis more rapidly than lactate and it needs less O[2] and produces less CO[2]. Ringer acetate has also a great utility during cardiovascular surgery with cardiopulmonary bypass. We compared efficacy and safety of Ringer acetate versus lactate in preparing cardioplegic solution during mitral valve surgery

Methods: 42 adult patients undergoing mitral valve replacement using CPB were randomly divided into two groups. Patients in group A received antegrade cold Ringer Acetate cardioplegic solution at a rate of l0ml/kg followed after 20 minutes by 5ml/kg retrogradely in the coronary sinus. Patients in group B received cold Ringer Lactate cardioplegic solution in a similar regimen to group A

Results: troponin I level from coronary sinus during reperfusion, was higher in group B than A [4.4+/-l.6ng/ml and 3.4+/-1.49ng/ml respectively] and after 4 and 24 hours postoperatively there was a significant increase in the serum Troponin I level in group B than In group A [p<0.05]. Lactate in the coronary sinus was higher in group B than A during rewarming [2.8+/-1.9ng/ml and 1.6+/-1.8ng/ml respectively]. The serum level was always higher in group B than A in the postoperative period [p<0.05]. There was no significant difference between both groups as regards the post-bypass ischemic changes as detected by TEE examination. Also, there were no differences in the duration of inotropic support, ventilation time, intensive care unit or hospital stay in the two groups

Conclusion: both Ringer Acetate and Lactate cardioplegia provide adequate myocardial protection, however the recovery of the heart from ischemia after the Ringer Acetate cardioplegia is better than Ringer Lactate