Derrick G P, Narang I, White P A, Kelleher A, Bush A, Penny D J, Redington A N
Great Ormond Street Hospital for Children, London, UK.
Circulation. 2000 Nov 7;102(19 Suppl 3):III154-9. doi: 10.1161/01.cir.102.suppl_3.iii-154.
Impaired right ventricular function has been implicated as a cause of reduced maximal exercise capacity after the Mustard operation for transposition of the great arteries.
Fourteen asymptomatic survivors of the Mustard operation were studied. Each underwent conventional cardiac catheterization, and after satisfactory hemodynamics were confirmed, load-independent indexes of ventricular function were derived by conductance catheter during dobutamine infusion (0, 5, and 10 microg x kg(-1) x min(-1)). Seven patients also underwent upright exercise testing on a bicycle ergometer with analysis of respiratory gas exchange by continuous mass spectrometry. Accessible pulmonary blood flow was measured at each workload with an automated acetylene rebreathing technique. All patients exercised to a satisfactory end point (respiratory quotient >1.1). Maximum oxygen consumption during exercise was impaired compared with predicted values (mean, 77%; P:<0.02). Both exercise and dobutamine infusion were associated with an increase in cardiac index and heart rate and a reduced stroke volume index response. This was despite significantly improved indexes of myocardial contraction (end-systolic pressure volume relation, P:<0.001), preload recruitable stroke work index (P:<0.01), VA coupling (P:<0.001), and isovolumic relaxation (P:<0.001) during dobutamine infusion. There were no changes observed in end-diastolic pressure-volume relations, but there was failure to augment ventricular filling manifest by absence of change in dV/dt (P:=NS).
The stroke volume response to exercise stress is reduced in patients after the Mustard operation. A similar failure to augment stroke volume occurs during dobutamine stress despite appropriate responses in load-independent indexes of contraction and relaxation. This is due to failure to augment right ventricular filling rates during tachycardia, presumably as a result of impaired AV transport, consequent to the abnormal intra-atrial pathways.
右心室功能受损被认为是大动脉转位Mustard手术后最大运动能力降低的一个原因。
对14名Mustard手术无症状幸存者进行了研究。每位患者均接受了传统的心导管检查，在确认血流动力学满意后，通过在多巴酚丁胺输注期间（0、5和10μg·kg⁻¹·min⁻¹）使用电导导管得出心室功能的负荷独立指标。7名患者还在自行车测力计上进行了直立运动测试，并通过连续质谱分析法分析呼吸气体交换。在每个工作负荷下，使用自动乙炔再呼吸技术测量可获得的肺血流量。所有患者均运动至满意的终点（呼吸商>1.1）。与预测值相比，运动期间的最大耗氧量受损（平均值为77%；P<0.02）。运动和多巴酚丁胺输注均与心脏指数和心率增加以及每搏量指数反应降低有关。尽管在多巴酚丁胺输注期间心肌收缩指标（收缩末期压力-容积关系，P<0.001）、可募集前负荷每搏功指数（P<0.01）、心室动脉耦合（P<0.001）和等容舒张（P<0.001）有显著改善，但仍出现上述情况。舒张末期压力-容积关系未观察到变化，但由于dV/dt无变化表明心室充盈未能增加（P=无显著性差异）。
Mustard手术后患者对运动应激的每搏量反应降低。尽管在多巴酚丁胺应激期间收缩和舒张的负荷独立指标有适当反应，但每搏量仍未能增加。这是由于心动过速期间右心室充盈率未能增加，推测是由于异常心房内途径导致房室传导受损所致。
