Peak oxygen uptake during exercise in mitral stenosis with sinus rhythm or atrial fibrillation: lack of correlation with valve area. A study in 70 patients

Remarkable oxygen consumption improvement after auricular flutter ablation in a patient with constrictive pericarditis and severe mitral stenosis

Atrial function is a key factor in cardiac output and oxygen consumption (VO₂). Substantial improvements in VO₂ have been reported after restoring sinus rhythm (SR) in patients with atrial fibrillation. However, there are no published data on how atrial function affects VO₂ in patients with both constrictive pericarditis (CP) and severe mitral stenosis (MS). A 53-year-old caucasian patient consulted for exacerbated heart failure (EHF). His medical record lists ischemic heart disease, severe MS, and CP after thoracic radiotherapy. The electrocardiogram showed atrial flutter (AFL) with controlled ventricular rate. Normal left ventricular ejection fraction was observed. Ergospirometry showed an impaired maximum VO₂ (VO₂ max) of 6 ml/kg/min. On the electrophysiological study typical AFL was diagnosed and ablated achieving a great exercise capacity improvement, correlated with an increase of VO₂ max to 16 ml/kg/min a week after ablation, and disappearance of EHF symptoms. This case illustrates how restoration of SR resulted in a clinical substantial improvement. Radiofrequency catheter ablation is warranted as the most effective option in this context. <Learning objective: Atrial function impairment has a marked impact on cardiac dynamics in patients with both severe constrictive pericarditis and mitral stenosis. In this setting, sinus rhythm restoration should be pursued.>.

Stress testing in valvular heart disease: clinical benefit of echocardiographic imaging

Symptom development represents one of the most important indications for surgical intervention in patients with significant valvular heart disease. Exercise testing has an established role in the assessment of exercise capacity and symptomatic status in patients with severe valvular heart disease who claim to be asymptomatic. In these patients, clinical decision can be influenced by the results of exercise testing. In addition to the assessment of symptomatic response to exercise, stress echocardiography can provide valuable information on exercise-induced changes in valve hemodynamics, ventricular function and pulmonary artery pressure. Abnormal left ventricular response to exercise, increase in pulmonary pressure or change in the hemodynamic severity of the valvular disease adds to the prognostic value of elicited symptoms. In this article we discuss the validated indications, proven prognostic values and potential influence on clinical decisions of stress echocardiography in left valvular heart diseases.

Mechanism of improvement in exercise capacity after the maze procedure combined with mitral valve surgery

OBJECTIVE

To clarify the mechanism of improvement in exercise capacity after the maze procedure.

DESIGN

Retrospective study.

SETTING

Tertiary referral centre.

PATIENTS

26 patients (mean (SD) age 57 (9) years) with atrial fibrillation (AF) and mitral valve disease were studied with echocardiography and cardiopulmonary exercise testing before and after the maze procedure combined with mitral valve surgery. Of these, eight had persistent AF and 18 had restored sinus rhythm (SR) by the surgery. Six patients (mean (SD) age 59 (12) years) with AF undergoing mitral valve surgery without the maze procedure who had cardiopulmonary exercise testing before and after the surgery formed the control group.

MAIN OUTCOME MEASURES

Echocardiographic parameters of atrial function were measured from transmitral flow recordings. Peak oxygen uptake (VO2) and the slope of the relation between VO2 and workload (ratio of DeltaVO2 to Delta work) were determined as indices of exercise capacity.

RESULTS

The degree of improvements in peak VO2 and the ratio of DeltaVO2 to Delta work after the mitral valve surgery was comparable between the maze and control group. It was also comparable between patients with and those without successfully restored SR after the maze procedure. The degree of the increase in peak VO2 correlated with the change in left atrial diameter (r = -0.40, p = 0.047) but atrial contraction did not correlate with the increase.

CONCLUSIONS

Improvement in exercise capacity may not be caused by restored SR and atrial contraction but may at least partly relate to the reduction of left atrial size and improvement of haemodynamic variables by the surgery.

Proteomics of heart disease

Heart diseases resulting in heart failure are among the leading causes of morbidity and mortality in developed countries. The underlying molecular causes of cardiac dysfunction in most heart diseases are still largely unknown, but are likely to result from underlying alterations in gene and protein expression. Proteomics now allows us to examine global alterations in protein expression in the diseased heart and will provide new insights into cellular mechanisms involved in cardiac dysfunction and should also result in the generation of new diagnostic and therapeutic markers. In this article we review the current status of proteomic technologies and describe how these are being applied to studies of human heart disease.

Does balloon mitral valvuloplasty improve cardiac function? A mechanistic investigation into impact on exercise capacity

Procedural technical success of balloon mitral valvuloplasty (BMV) is indicated by an increase in valve area and a reduction in transvalvar gradient, but there are conflicting results regarding whether these indicators correlate with subsequent improvements in exercise capacity. We conducted a study to explore the effects of valvuloplasty on cardiac function to gain insight into the mechanisms responsible for the impact on exercise ability. Sixteen patients with mitral stenosis participated in the study and the five who did not proceed to valvuloplasty served as the control group. All patients performed maximal cardiopulmonary exercise tests before and 6 weeks after valvuloplasty (without valvuloplasty in controls). Central haemodynamics including cardiac output were measured non-invasively at rest and peak exercise. At baseline, the cardiopulmonary exercise test results were similar in the two groups. Following valvuloplasty, cardiac output did not alter at rest, but increased significantly at peak exercise (8.7+/-1.7 to 10.5+/-2.1 l min(-1), P<0.01), as did peak cardiac power output (1.88+/-0.55 to 2.28+/-0.74, P<0.05) and cardiac reserve (1.07+/-0.33 to 1.45+/-0.55 watts, P<0.05). Aerobic exercise capacity improved (13.9+/-4.2 to 16.4+/-4.3 ml kg(-1) min(-1), P<0.01) as did exercise duration (354+/-270 to 500+/-266 s, P<0.01). There were no significant changes in the controls. There was a significant correlation between the changes in peak VO(2) and changes in cardiac reserve (r=0.62, P<0.01) but not with changes in resting haemodynamics. These changes did not correlate with changes in peri-procedural mitral valve haemodynamics, despite increases in mitral valve area from 1.05+/-0.16 to 1.74+/-0.4 cm(2) (P<0.0001), accompanied by falls in the transvalvar gradient and pulmonary artery pressure (12.4+/-4.7 to 4.5+/-3 mmHg, and 26.8+/-8.4 to 17.4+/-5.2 mmHg, respectively, all P<0.0001). In conclusion, we found that successful mitral valvuloplasty in our patient cohort led to improved cardiac and physical functional capacity but not resting haemodynamics. Neither indicators of technical success nor resting haemodynamics were very reliable in predicting functional improvement.

[Mitral stenosis]

The decrease in the incidence of acute rheumatic fever in western countries has led to a sharp decrease in the incidence of mitral stenosis. This decrease also modifies the clinical presentation and mitral stenosis is now encountered in older patients who have severe impairment of valve anatomy. In developing countries, mitral stenosis remains a frequent disease. The management of patients with mitral stenosis has been modified by the development of percutaneous mitral commissurotomy whose safety and efficacy have been demonstrated in a number of studies with a follow-up of up to ten years. Percutaneous mitral commissurotomy is now the reference treatment for mitral stenosis with pliable valves in young patients and its efficacy has been validated in randomised trials versus surgery. Mitral stenosis in older patients, as it is encountered in western countries, is a more heterogeneous group. Predictive analysis has shown that the predictions of immediate and late results are multifactorial. This has led to consider the indications for percutaneous mitral commissurotomy in patients who do not have ideal anatomic conditions, when their other characteristics are favourable. This is particularly the case in young patients who do not have a very tight mitral stenosis (1-1.5 cm2) and who do not have an advanced heart disease. When the conditions are favourable, percutaneous mitral commissurotomy can be considered in patients who have few symptoms, in particular in order to reduce the thromboembolic risk.

Effect of inadequate cardiac output reserve on exercise tolerance in patients with moderate mitral stenosis

Twenty-nine patients with moderate mitral stenosis and 29 age-matched normal controls underwent symptom-limited upright bicycle exercise testing with simultaneous hemodynamic monitoring. Exercise tolerance in the mitral stenosis group was found to be limited by inadequate cardiac output reserve and not by resting mitral valve area or exercise pulmonary capillary wedge pressure.

[Usefulness of exercise Doppler in the diagnosis of severe mitral stenosis]

BACKGROUND

Exercise in mitral stenosis produces an increase in cardiac output and heart rate which determines the increment in the transmitral gradient. However, it has not yet been established what level is reached by the gradients on exercise in severe mitral stenosis nor whether the rise in the gradient during such exercise is different to that occurring in non-severe stenosis.

OBJECTIVE

To evaluate the effect of exercise in patients with severe mitral stenosis on the mitral valve gradients in absolute values and on the increment with respect to base values.

METHODS

Forty-eight mitral stenosis patients (mean age: 48.8 +/- 11 years) underwent 50 exercise Doppler echocardiographic studies using supine bicycle ergometry in two stages with increases of 25 W every 3 minutes; from each of these we obtained the peak and mean mitral gradient using a non-imaging continuous-wave Doppler probe. We also conducted this procedure on 14 patients with a mean age of 50 +/- 6 who had Bjork mitral prostheses which were functioning normally.

RESULTS

We defined a hemodynamic profile of severity based on the data from 18 patients whose basal mitral valve areas was < 1.2 cm2 (group I), and compared them with the data from the 32 studies of mitral stenosis patients with an area > 1.1 cm2 (group II) and with the patients with mitral prostheses (group III). The mean mitral gradient (mmHg) in group I was greater than in group II at rest (9.3 +/- 3.2 and 6.6 +/- 2.7; p < 0.001), at 25 W (20.6 +/- 4.8 and 14.1 +/- 5; p < 0.001) and at 50 W (25.9 +/- 5.4 and 17.3 +/- 5.8; p < 0.001). The increase in mean mitral gradient from the baseline to 50 watts was 16.7 +/- 4.5 mmHg in group I, which was greater than in group II and III (11.1 +/- 4.1 and 6.8 +/- 2.6 mmHg; p < 0.001).

CONCLUSIONS

Exercise Doppler echocardiography enabled us to define a differential hemodynamic profile in patients with severe mitral stenosis which can be used in isolation as an indicator of severity in this condition.

Factors determining the exercise capacity in mitral stenosis

In mitral stenosis, peak pulmonary pressure after exercise rather than valve area at rest or mitral gradient, was found to be an important factor in determining the exercise capacity.