The ‘A-dip’ of diastolic mitral regurgitation: An unusual Doppler flow pattern in a patient with severe aortic insufficiency and complete heart block
Department of Cardiology Echocardiography Laboratory, New York University Medical Center, 560 First Avenue, New York, NY 10016, USA
Received 28 July 2006; accepted after revision 29 August 2006; online publish-ahead-of-print 7 November 2006.
* Corresponding Author. Tel: +1 212 263 5665; fax: +1 212 263 8461. E-mail address: itzhak.kronzon{at}med.nyu.edu
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Abstract |
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This is an unusual case of diastolic mitral regurgitation (MR) with a high diastolic velocity jet and prolonged jet duration related to a combination of acute severe aortic insufficiency and high-degree atrioventricular block. This case illustrates an interesting hemodynamic phenomenon with multiple transient decreases in the pressure gradient between the left ventricle and left atrium during diastole related to a temporary increase in left atrial pressure associated with atrial contraction.
Keywords: Diastolic mitral regurgitation; Aortic insufficiency; Atrioventricular conduction block
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Case report |
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TopAbstractCase reportTransthoracic echocardiogramDiscussionReferences |
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A 41-year old man presented to the Emergency Room with several hours of worsening dyspnea at rest, dizziness, and emesis. Physical examination revealed a blood pressure of 85/58 and a heart rate of 40 beats/min. Cardiac examination demonstrated a high-pitched III/VI systolic murmur heard best at the upper left sternal border that radiated throughout the precordium. Lungs were clear to auscultation. ECG exhibited high-degree atrioventricular block with a ventricular escape rhythm of 40 beats/min and an atrial rate of 90. The patient was evaluated by transthoracic echocardiography.
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Transthoracic echocardiogram |
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There was mild concentric left ventricular (LV) hypertrophy with normal LV wall motion and ejection fraction. Mild left atrial (LA) and LV dilatation were present. Mild aortic root dilatation and a thickened aortic valve with normal leaflet excursion were visualized. M-mode revealed mitral valve closure early in diastole without reopening with atrial contraction during the markedly prolonged diastolic period (Figure 1).
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Severe aortic regurgitation (AR) was demonstrated by color flow Doppler and the fast deceleration of the aortic regurgitation jet on continuous wave Doppler. A moderate degree of systolic mitral regurgitation (MR) was noted by color flow Doppler. An elevated LV end-diastolic pressure of 42 mmHg was determined by calculating the difference between the end-diastolic pressure gradient on the AR continuous wave Doppler tracing and the aortic diastolic pressure (measured by cuff).
Diastolic MR was documented by color flow Doppler imaging (Figure 2) and on continuous-wave Doppler (Figure 3). The duration of diastolic MR was significantly prolonged secondary to the patient's high-degree atrioventricular block, which caused an unusually long diastole. The diastolic MR had a velocity of 3 m/s that transiently decreased to 2 m/s with each atrial contraction. The LV pressure gradient during diastole was calculated to be 36 mmHg throughout most of diastole and transiently decreased to 16 mmHg with atrial contraction. This gradient correlated with an LA pressure between 6 mmHg during diasthesis and 26 mmHg with atrial contraction.
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Discussion |
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TopAbstractCase reportTransthoracic echocardiogramDiscussionReferences |
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Diastolic MR has been described in the setting of severe, acute AR, atrioventricular block of any degree, and in the presence of restrictive ventricular physiology. It typically occurs in mid to late diastole in the setting of premature and incomplete closure of the mitral valve and elevated LV diastolic pressure that exceeds LA pressure during ventricular diastole. Diastolic MR typically has a relatively low velocity of 2 m/s or less secondary to a relatively low diastolic LV–LA pressure gradient.
The normal closure of the mitral valve is typically thought to occur at the onset of systolic isovolumetric LV contraction when the LV pressure exceeds that of the LA. However, there are multiple components that are required for effective and complete mitral closure to occur at the end of diastole. Normally, atrial contraction transiently increases the LA diastolic pressure above that of the LV diastolic pressure and results in wide opening of the mitral valve at end diastole. Toward the end of atrial contraction there is an abrupt cessation of forward flow leading to a transient zone of negative pressure behind the mitral valve and the formation of eddy currents behind the leaflets that precipitates closure of the mitral valve.1 The LA then relaxes as LV pressure rises leading to closure of the mitral leaflets. An effective and appropriately timed ventricular systole is then required for isovolumetric contraction and effective sealing of the mitral valve.
If the LV diastolic pressure rises abruptly and exceeds that of LA diastolic pressure, as may occur with acute AR, the mitral valve may close prematurely (Figure 4). If, at this point, the mitral valve is incompetent, it can result in diastolic retrograde flow between the LV and LA, defined as diastolic MR. Furthermore, diastolic MR can occur in the setting of conduction abnormalities during which time the LV–LA pressure gradient is prolonged due to the delay in ventricular systole.2
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Although this phenomenon has been described previously, this patient's echocardiographic findings were remarkable because the combination of severe AR and high degree AV block resulted in an unusually prolonged duration of the LV–LA pressure gradient. This pressure gradient was demonstrated by a continuous-wave Doppler tracing that revealed multiple unusual transient decreases in the pressure gradient during this diastolic period. Caused by the temporary increase in LA pressure with atrial contraction, these unusual ‘atrial dips’ reflect a transient increase in left atrial pressure from 6 to 26 mmHg.
This case was also remarkable because it clearly demonstrates the protective function of the premature closure of the mitral valve. Although this patient's left ventricular diastolic pressure was markedly elevated, the LA pressure remained low throughout most of diastole. The left atrial pressure was able to remain low because the elevated left ventricular diastolic pressure quickly exceeded the left atrial diastolic pressure and led to premature closure of the mitral valve. As demonstrated on M-mode echocardiography (Figure 1), this markedly elevated LV end diastolic pressure prevented the usual transient opening of the mitral valve with atrial contraction as is often seen in premature closure of the mitral valve associated with high-degree AV block when the LA pressure temporarily exceeds that of LV diastolic pressure with atrial contraction. It was this protective effect of the premature closure of the mitral valve that prevented the patient from developing pulmonary edema.
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References |
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- Panidis I, Ross J, Munley B, Nestico P, Mintz G. Diastolic mitral regurgitation in patients with atrioventricular conduction abnormalities: A common finding by Doppler echocardiography. J Am Coll Cardiol (1986) 7:768–74.[Abstract]
- Downes T, Nomeir AM, Hackshaw BT, Kellam LJ, Watts LE, Little WC. Diastolic mitral regurgitation in acute but not chronic aortic regurgitation: Implications regarding the mechanism of mitral closure. Am Heart J (1989) 117:1106–12.[CrossRef][Web of Science][Medline]
- Agmon Y, Freeman W, Oh JK, Seward JB. Diastolic mitral regurgitation. Circulation (1999) 99:e13.
[Free Full Text] - Schnittger I, Appleton C, Hatle LK, Popp RL. Diastolic mitral and tricuspid regurgitation by Doppler echocardiography in patients with atrioventricular block: new insight into the mechanism of atrioventricular valve closure. J Am Coll Cardiol (1988) 11:83–8.[Abstract]
- Utsunomiya T, Gardin J. Observations on Doppler mid-diastolic mitral flow reversal. J Am Soc Echocardiogr (1991) 4:361–6.[Medline]
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