RELATIONSHIP OF RED CELL CONCENTRATION AND SIZE TO THE PRESENCE AND SEVERITY OF LEFT ATRIAL SPONTANEOUS ECHO CONTRAST IN MITRAL STENOSIS
R E Peverill, R W Harper, L Yates and JJ Smolich
Centre for Heart and Chest Research, Department of Medicine, Monash Medical Centre and Monash University, Clayton, Victoria
Red cell aggregation occurring in conditions of sluggish blood flow is the underlying mechanism for the development of left atrial spontaneous echo contrast (LASEC), and the level of haematocrit (Hct) has been shown to be positively associated with the presence of LASEC in atrial fibrillation (AF). While Hct is determined by the product of red cell count (RCC) and mean corpuscular volume (MCV), the relative contributions of RCC and MCV to the presence and severity of LASEC are unknown. To address this question, this study examined the relationship of RCC and MCV with LASEC in 112 patients with mitral stenosis (46 with AF) who underwent transoesophageal echocardiography to grade LASEC (0-4) and cardiac catheterisation to measure haemodynamics.
Patients with LASEC were more likely to have AF (p<0.04), a lower cardiac index (CI; p<0.01) and a higher Hct (p<0.04) and MCV (p<0.04), but had a similar RCC to those without LASEC. Only AF was an independent predictor of the presence of LASEC. On univariate analysis, the grade of LASEC was positively correlated with AF (r=0.5) and left atrial diameter (LAD; r=0.33), and negatively correlated with mitral valve area (MVA; r=0.37) and CI (r=0.43). LASEC grade was positively correlated with Hct (r=0.25) and RCC (r=0.18), but not MCV, although there was a strong negative correlation between RCC and MCV (r=0.51), and when included together, RCC and MCV made independent contributions to LASEC grade. The best multivariate clinical and haemodynamic model of LASED grade comprised AF, MVA and mitral regurgitation (MR) with a borderline significant contribution of LAD. No improvement in any clinical model which included AF or CI was apparent when RCC or Hct was added, in part due to collinearity between these variables. In the subgroup of patients with sinus rhythm the best model included MVA, MR and RCC (r2=0.20), while in AF the best model contained MVA, MR and LAD (r2=0.33).
Conclusion: These findings suggest that, in mitral stenosis, there is a complex relationship of LASEC with RCC and MCV which is influenced by the association of these red cell indices with both cardiac rhythm and CI.
