Open-heart techniques and mitral valve plasty for mitral regurgitation in toy- and small-breed dogs: A review

In human medicine, in the past, open-heart techniques for low-bodyweight children and newborn babies with congenital heart disease were more difficult than high-bodyweight adults. In toy- and small-breed dogs with mitral regurgitation (MR), an acquired heart disease, these techniques are more difficult to perform than for congenital heart diseases in young medium-sized or large dogs because of old age and low body weight. Therefore, improved open-heart techniques and mitral valve surgery for severe MR in older toy- and small-breed dogs are essential. Through our surface-cooling hypothermia (sHT) studies, we designed a new, improved open-heart method, namely, “the low-flow cardiopulmonary bypass (CPB) combined with deep sHT in toy- and small-breed dogs (Japan method)”; sHT was later replaced by blood-cooling hypothermia (bHT). At the same time, we devised a new, improved mitral valve plasty (MVP) applicable to severe MR, instead of mitral valve replacement, in toy- and small-breed dogs. This MVP technique was combined with artificial chordal reconstruction, semi-circular suture annuloplasty (AP), and direct scallop-suture valvuloplasty. These MVP techniques are simple, durable, and lead to good long-term quality of life in toy- and small-breed dogs. This review highlights the benefits of our improved CPB and MVP techniques (Japan method) for severe MR in toy-and small-breed dogs, which have led to a high success rate for MVP in severe clinical MR cases in Japan. It may further contribute to the development of more robust techniques for MR in toy- and small-breed dogs. This also represents the first comprehensive review of the history of open-heart surgery, CPB techniques, and MVP methods for MR in toy- and small-breed dogs.

Utility of coherent and ripple mapping for post-mitral valve plasty biatrial macro-re-entrant tachycardia: a case report

Background Biatrial tachycardia (BiAT) is a rare form of atrial macro-re-entrant tachycardia. Precise identification of interatrial connections and circuits of the BiAT is difficult. And incomplete understanding of the re-entrant circuit may lead to unnecessary ablation, thus increasing the risk of complications. Case summary A 69-year-old man with a history of mitral valve plasty for mitral regurgitation due to mitral valve prolapse was admitted for persistent atrial tachycardia. Electrophysiological examination using the CARTO mapping system was performed. A coherent map revealed an atrial tachycardia with a cycle length of 304 ms and a re-entrant circuit involving the left atrial septum and right atrial septum, while a ripple map suggested an epicardial interatrial connection between the right atrium and left atrium. Radiofrequency ablation on the epicardial connection successfully terminated BiAT without complications. Discussion In BiAT using both atrial septum as a re-entrant circuit, an interatrial connection or an atrial septum can be the target site for ablation. However, septal ablation can be challenging because of the risk of atrioventricular block or interatrial conduction delay, and minimal line or point ablation is needed. Coherent and ripple mapping can accurately determine the re-entrant circuit and interatrial connection of BiAT and reduce complication risks by terminating the atrial tachycardia with minimal ablation.