Right atrial contractile performance in patients with myocardial infarction

To evaluate right atrial (RA) contractile performance in patientswith myocardial infarction, we validated a cineangiographicmethod of RA volume measurement, and investigated RA volumechange in ‘normal’ individuals and patients witha previous myocardial infarction. Sixteen silicone rubber RAcasts made from human cadavers were filmed in the postero-anteriorand left lateral projections. The cast volumes calculated followingSimpson's rule were in good agreement with those measured bywater replacement (r=0.992, P<.001). At cardiac catheterization,biplane RA cineangiography was performed in 19 ‘normal’individuals (N group), in 14 patients with a previous antero-septalinfarction (AM1 group) and in seven patients with apreviousinferior infarction (IMI group). The RA volume-time curve wasconstructed at 20–40 ms intervals for one cardiac cycle.RA volume at the beginning of the atrial contraction (RAVd),which was defined as the ‘preload’ of the RA, tendedto be larger in both the AMI and IMI groups compared with ‘normal’individuals. The RA ejection volume was significantly largerin both the AMI (18.4 ± 2.1 ml. m^–2, P <0.01)and IMI groups (l9.4±2.8, P<0.01) than in the N group(14.5±1.9), even for a comparable level of RAVd (rangefrom 26 to 36ml.m^–2) (18.6±2.1, P<0.01, 18.2±2.0,P<0.01, 14.7±1.9, respectively). These results suggestthat RA contraction increases in patients with myocardial infarctionby increasing both the ‘preload’ and ‘contractility’of the RA.