Brain M T

etic Resonance Imagmg Before and After Percutaneous Mitral Ba loon Commissurotomy Paulo Rocha, MD, Robert Mulot, MD, Pascal Lacombe, MD, Rkmy Pikre, MD, Abdel Belarbi, MD, and Bernadkte Raffestin, MD

I n western countries before 1990, strokes complicated 3% to 4% of percutaneous mitral balloon commis-

surotomy (PMBC) procedures.*,* With the generalized use of transesophageal echocardiography-a more sen- sitive technique than transthoracic echocardiography to detect left atria1 thrombi3-stroke frequency has been reduced. However, the common linding of thrombi between the 2 balloons of the bifoil catheter, when pulled back after the procedure,4 prompted us to search for minor stroke signals on brain magnetic resonance imag- ing (MRI) in patients without clinical evidence of brain embolism.

Twenty-six women and 1 man (aged 48 f 16 years) underwent PMBC. In each patient, 2 successive brain MRIs were performed: I ~48 hours before, and the oth- er up to 48 hours after, the procedure. Twelve patients were in class II and 1.5 in class III of New York Heart Association functional classification. Mitral valve area, assessed by transthoracic 2-dimensional echocardiog- raphy, Doppler, or Gorlin’s hemodynamic formula, was cl.5 cm2 in every patient. Sinus rhythm was present in 18 patients. None had previous clinical signs of brain embolism. Three patients had had closed mitral com- missurotomy 10,13, and 21 years ago, respectively. The echocardiographic mitral valve scores was 8 + 2, and mitral regurgitation on left ventriculography was l+ in 9 patients and 2+ in 4.

Transesophageal echocardiography was performed in every patient within 48 hours before mitral dilation. In our PMBC technique, which has already been exten- sively described,6 the balloon crosses the stenotic valve on the anterograde route by transseptal catheterization in all cases. Previous anticoagulation treatment was usu- ally stopped before the procedure, and 0.7 mglkg of heparin was administered intravenously after transsep- tal catheterization. Inoue balloons (28 or 30 mm) were

From the Departments of Physiology, Radiology, and Cardiology, Hbpi- tal Ambroise Pan?, Universitd de Paris RenC Descartes, Service Central d’Explorations Fonctionnelles, 9 Avenue Charles de Gaulle, 92104 Boulogne Billancourt, France. Manuscript received March 23, 1994; revised manuscript received and accepted June 6, 1994.

initially used in 14 patients and bifoil (Twin-AT Mans- field) balloons in 13. A bifoil balloon was replaced 4 times by an Inoue balloon because of bifoil instability. The procedure was successful for the entire group, and mitral valve area, assessed by 2-dimensional echocar- diography, Doppler, or hemodynamics was ~1.5 cm2 in each patient. Hemodynamic data are presented in Table I. These results are similar to results obtained in our 320 previous patients.

Brain MRI was pevformed using a median jeld (0.5 Tesla) with axial slices 8 mm in depth. The sequence, similar for all patients, was: SE T2-weighted magnetic resonance images (relaxation time = 2,020 ms, echo time = 60 to 120 ms).

Data are presented as mean f SD. Comparisons were analyzed using Student’s paired t test. A p value co.05 was considered significant.

Hyperintensity foci suggesting brain embolism (multi- ple or isolated and ~1 cm for all patients but 1) were found in 22 of 27patients before PMBC. After mitral dila- tion, new hyperintensity foci were found in 11 of 27 patients (Figure 1): 4 were in atria1 fibrillation and had previous anticoagulation treatment, and the 7 remaining patients were in sinus rhythm without this treatment. These new hyperintensity foci were again ~1 cm and patients were asymptomatic. One patient had 2 locations in the brain. These new hyperintensity foci were as frequent with the bifoil(6 of 14) as with the Inoue (5 of 13) balloon.

Peripheral embolism during PMBC seems to be less frequent in the oriental than in the western world. It was never reported in studies by Chen et al7 or by Nobuyoshi et al8 and concerned only 1% of Hung’s patients.9 This lower stroke frequency may be related to ethnic features, but also to earlier availability of Inoue’s balloon (1984). Indeed, in western countries, strokes became scanty after the arrival of this balloon (1990). Given its characteris- tics, Inoue’s balloon requires less left atria1 maneuvers, often the cause of thrombi displacement or fragmenta- tion, and it shortens the procedure. Brain embolism is also rare when mitral dilation is performed without transseptal catheterization, and it was never observed by Stefanidis et allo in 85 PMBCs.

TABLE I Hemodynamic Data of 27 Patients Undergoing Percutaneous Mitral Balloon Commissurotomy

mPA mLA

(mm Hg) (mm Hg)

Grad.

(mm Hg)

Hemody. MVA

(cm?

2-D Echo Doppler MVA MVA

(cm”) (cm’) Qp/Qs

Before PMBC 33 22 16 1.06 1.04 0.91 kll +7 +7 20.19 kO.29 So.26

After PMBC 26 13 5 2.32 2.17 2.08 1.20 +10* ?r7t +3* ko.49’ f0.58* kOo.47* kO.23

*p <0.05; ‘p <O.OOi ; *p <0.0001. 2-D Echo = 2-dimensional echocardiography; Grad. = mean diastolic pressure gradient between left ventricle and left

atrium; Hemody. = hemodynamic; mLA = mean left atrial pressure; mPA = mean pulmonary arterial pressure; MVA = mitral valve area; PMBC = percutaneous mitral balloon commissurotomy; Qp/Qs = pulmonary to systemic flow ratio. 1

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Hyperintensity foci are not exclusively induced by embolisms and may be linked to many other pathologies (Table II). They are often observed in demyelinizated perivascular areas, particularly in elderly and hyperten- sive patients. To distinguish between new and old em- bolisms, a brain MRI was performed before the proce- dure as well; the short delay between the 2 MRIs thus makes embolisms the most likely explanation of new hyperintensity foci. However, 2 conditions deserve analy- sis: hypotension and senility. Balloon inflation, in par- ticular with balloons of cylindrical profile such as Inoue’s balloon, dramatically limits left ventricular fill- ing, with consequent hypotension. Nevertheless, with Inoue’s balloon, inflation plus deflation can be accom- plished in 10 seconds. Bifoil inflation plus deflation time is much longer, sometimes going beyond 1 minute, but left ventricular filling is still possible through the gaps between the 2 balloons; in fact, hypotension ~60 mm Hg was rare in this group. Therefore, we do not believe that the 11 new hyperintensity foci could have been caused by hypotension. Brain hypersignals (like hypo- signals) are also often detected in healthy elderly pa- tients, mostly in the white matter.“*‘* Since in the pres- ent study, the new hyperintensity foci appeared within 4 days, it is unlikely that they were related to senility; moreover, the mean age of our group was 48 years, with only 2 patients aged >70 years.

Hyperintensity foci were observed in 22 patients before PMBC: most of these patients had multiple hyper- intensity foci with a diameter <l cm in all but 1. This latter patient had an important unihemispherical defect, the aftermath of a neonatal anoxic period. Mitral steno- sis is an embolizing pathology and the high rate of hyper- intensity foci before PMBC is not astonishing.

The new hyperintensity foci, consistent with peripro- cedural embolisms, had a diameter <l cm and were not followed by any clear neurologic symptom. One patient from this group, with a double location in the corpus cal- losum (genu and splenium), had a convulsive fit, need- ing a short and light general anesthesia before transsep- tal catheterization. Embolism was simultaneous with diagnostic catheterization in this case and may not be related to the PMBC procedure itself. Nevertheless, brain MRIs were performed in 3 other patients before and after a conventional diagnostic catheterization, and the second brain MRI did not disclose new hyperinten- sity foci.

Strokes during PMBC seem less dramatic than strokes induced by atherosclerosis. Death by stroke’ in published reports on PMBC is uncommon. Because the 8 patients with brain embolisms reported by Vahanian et al2 quickly recovered all functions, the investigators concluded that these transient strokes could be provoked by gas embolism. In the present study, balloon rupture was never observed. In our prior 320 PMBC procedures, 7 patients had clinical signs of brain embolism: 5 before, but only 2 since, the systematic use of transesophageal echocardiography. One month after PMBC, neurologic clinical signs persisted in only 2 of the 7 patients.

After the introduction of transesophageal echocardi- ography’ in 1990, left atria1 thrombi were detected in 4 patients. All 4 thrombi images vanished after 2 months

TABLE II Possible Hypersignal Etiologies in Brain Magnetic Resonance Imaging

of warfarin treatment, and PMBC was successfully per- formed in all patients. In 1989, massive hemiplegia with aphasia and convulsive fits complicated PMBC. Previ- ous transthoracic echocardiography of this 47-year-old patient had not disclosed atria1 thrombi. However, on the left atria1 angiogram recorded after the procedure to assess a possible residual atria1 septal defect, a bulky thrombus was clearly detected in the left appendage. Small moving fresh thrombi could be observed attached to the main thrombus. The clinical evolution of this patient was excellent: she was able to walk the next day and was paucisymptomatic 6 months after. The favor- able evolution of these patients may be explained by their younger age and by a prior normal cerebral vascular net- work.

Brain embolism is not rare during PMBC and appears related to the procedure itself. In this group of patients, brain embolisms were not accompanied by symptoms, were not more frequent in patients with atrial fibrillation or without previous anticoagulation treatment, and were not related to balloon type. Hypersignals in brain magnetic resonance images had a diameter cl cm. Undetected previous left atria1 thrombi or clotting over the catheter balloon may be the origin of these embolisms.

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