Factors affecting immediate changes in cardiac output following balloon mitral valvulotomy: the role of pulmonary hemodynamics.
OBJECTIVE
The study aim was to investigate the factors that affect changes in cardiac output (CO) following balloon mitral valvulotomy (BMV), which at present are essentially unknown.


METHODS
Among a total of 168 patients, clinical, echocardiographic and hemodynamic data before and after BMV were compared between patients in group I (<15% increase in CO after BMV) and group II (>15% increase). A multiple logistic regression analysis was used to identify factors that were predictive of an increase in CO.


RESULTS
Before BMV, the mean CO was 3.9 +/- 0.9 and 4.1 +/- 0.71/min (p = NS) in groups I and II, respectively. Group I patients were more symptomatic, with a greater proportion in NYHA class > or =3. The pulmonary artery mean pressure (PAMP) was also higher in group I patients (51 +/- 20 mmHg) than in group II (35 +/- 12 mmHg) (p < 0.03). Pulmonary vascular resistance (PVR) was also higher in group I than in group II (6.9 +/- 3.6 and 4.0 +/- 3.0 Woods units, respectively; p < 0.02). Right ventricular function, left ventricular ejection fraction (LVEF), heart rate, mitral valve area, transmitral mean gradient, Wilkin's valve score and incidence of atrial fibrillation were similar in both groups. After BMV, the CO was 4.1 +/- 0.8 and 4.8 +/- 0.8 1/min (p < 0.005) in groups I and II, respectively. Likewise, there was similar inter-group increase in valve area and a decrease in mean gradient. The PAMP was reduced in both groups compared to pre-BMV, but remained higher in group I than in group II (35 +/- 17 and 21 +/- 9 mmHg, respectively; p < 0.05). PVR was decreased in group II and remained higher in group I (2.8 +/- 1.8 and 6.1 +/- 2.6 Woods units, respectively; p < 0.05). The magnitude of iatrogenic interatrial shunt was similar in both groups. Following BMV, a >50% fall in PVR was predictive of an increase in CO by 15% (OR 5.7, 95% CI 3.1-7.8).


CONCLUSIONS
Patients with a post-BMV increase in CO had a lower pre-procedure PAMP and PVR. In group I, a high PVR ('second stenosis') did not fall after BMV. In spite of an apparent overall improvement in hemodynamics, there was a suboptimal rise in CO. PAMP, despite a significant fall, remained higher than normal. The pulmonary hemodynamics were seen to influence changes in CO after BMV, despite similar changes in valve area and mean gradients, with similar Wilkin's scores and right ventricular function between the two groups. A fall of >50% in PVR is predictive of a post-BMV increase in CO.
Krishnamoorthy
K Mahadevan
KM
Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India. kmkm@sctimst.ac.in
Dash
Parbat K
PK
D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology*; D002404:Catheterization; D002648:Child; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000000981:diagnostic imaging; D008946:Mitral Valve Stenosis / Q000503:physiopathology / Q000628:therapy*; D011651:Pulmonary Artery / Q000502:physiology*; D014463:Ultrasonography; D014655:Vascular Resistance / Q000502:physiology*