Bicuspid Aortic Valve

Fig. 6.1
Diagram of the patient’s auscultation findings including a prominent ejection click, a diastolic crescendo decrescendo murmur and systolic decrescendo murmur

      Test Results

      • Electrocardiogram is normal (Fig. 6.2).
        A310603_1_En_6_Fig2_HTML.gif
        Fig. 6.2
        Normal electrocardiogram in the setting of BAV
      • Echocardiogram:
        • A BAV can be seen (Fig. 6.3).
          A310603_1_En_6_Fig3_HTML.jpg
          Fig. 6.3
          Echocardiogram showing BAV
        • Normal left ventricular size and function.
        • The aortic root diameter is upper normal (3.6 cm).
        • Echo Doppler shows mild AR and mild AS (2.1 m/s).

      Clinical Basics

      Definition

      • Most commonly, a BAV is associated with the congenital fusion of right and left coronary cusps, which is seen in 70–80 % of cases (Fig. 6.4). The other, less common fusion is of the right cusp and the posterior (noncoronary) cusp, which is seen in the other 20–30 % of cases [1].
        A310603_1_En_6_Fig4_HTML.gif
        Fig. 6.4
        There are several types of malformations characteristic of a bicuspid aortic valve
      • Median raphe is typically (60 %) in the conjoint cusp. Differential point for acquired bicuspid AV: Raphe does not reach cusp margin.

      Prevalence

      • BAV is a congenital disorder that affects 1–2 % of the population [2]. Males make up 70–80 % of cases. It is the most prevalent congenital heart abnormality.

      Etiology

      • BAV accounts for approximately half of all cases of AS, with a presentation typically in the 5th–6th decade. It also accounts for about one-fourth of all cases of AR, commonly presenting earlier in life.
      • A 2012 study of patients at necropsy found that 61 % of those with BAV had aortic stenosis [3, 4]. There is a significant association with aortic dilatation, with studies varying from 33 to 79 % prevalence depending on the study criteria. Increased risk for endocarditis has also been associated with BAV [4].
      • There does appear to be a significant genetic component to BAV. One epidemiological study showed a prevalence of 14.6 % of BAV in affected families, which is a much higher rate than the general population [5]. The risk of BAV among 1st degree relatives of an affected individual is 10 % [2]. A family history of BAV should raise suspicions during evaluation.
      • There is also a high association of BAV with other congenital anomalies including aortic coarctation, interrupted aortic arch, and other aortopathies [2].

      Signs and Symptoms

      • Commonly asymptomatic and may be found as an incidental finding on an echo for another reason.
      • Symptoms of BAV are related to the pathologies closely associated with the anomaly, including AR, AS, and aortopathies.

      Key Auscultation Features

      • There are several key auscultation features associated with BAV [6]. Table 6.1 describes the auscultation characteristics of the anomaly.
        Table 6.1
        Key auscultation characteristics associated with BAV
        Feature
        Description
        Ejection click [6–8]
        S1 is split in 85 % of cases
        Ejection click in BAV associated with aortic valve opening
         Halting of opening of AV
         Intensity equal to or greater than M1
         Intensity constant throughout respiration
         Heard over entire precordium
          At apex, true “splitting” of S1 is generally not audible
         Associated with a loud A2
         Short and sharp ejection “click”
         Timing:
          T1 <50 ms (pa-da)
          A1 >50 ms (pa-ta)
          Mitral/tricuspid closure represents non-pathological splitting
        Systolic murmur
         Early to mid systolic
         Flow related
        S2
         Increased 1.5–2 fold in uncomplicated BAV
         A decrease might suggest a degree of AS
        Diastolic murmur
         AR is common
         Frequently mild
        While the ejection click is most typical of BAV, systolic and diastolic murmurs in addition to alterations in S2 may be heard
      • It is important to differentiate between non-pathological splitting of S1 and a true ejection click. A true BAV ejection click is related to the halting of the opening of the aortic valve, and the sound occurs later than a typical split S1 (Fig. 6.5).
        A310603_1_En_6_Fig5_HTML.gif
        Fig. 6.5
        Phonogram of aortic ejection click heard in bicuspid aortic valve. Note the timing of the click relative to M1 and T1, distinguishing it from non-pathological splitting of S1. Note also the loud S2 (Used with permission from Leech et al. [6])
      • One should also note that the auscultatory hallmarks of BAV may vary depending on whether aortic stenosis or regurgitation is present.
      • Auscultation examples of bicuspid aortic valve.
        • Click here to listen to an example of bicuspid aortic valve showing an ejection click, with a mild (15 mmHg) gradient, and see an image of the phonocardiogram (Video 6.1).

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        Related posts:

        1. Aortic Sclerosis
        2. Introduction to Cardiac Auscultation
        3. Aortic Stenosis
        4. Mitral Stenosis

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      Jul 10, 2016 | Posted by in CARDIOLOGY | Comments Off on Bicuspid Aortic Valve

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