Page 33 - Read Online

Rao. Vessel Plus 2022;6:22 https://dx.doi.org/10.20517/2574-1209.2021.105 Page 21 of 24

Doppler studies demonstrate near-normal-sized LA and LV in small PDAs. Enlargement of the LA and LV
can be seen in patients with moderate to large PDAs; these changes are largely proportional to the size
(minimal ductal diameter) of the PDA. The LV contractile function, as evaluated by LV fractional
shortening and ejection fraction, is normal initially and may become hyper-contractile with time. When
severe myocardial dysfunction due to prolonged and/or large shunt occurs, LV contractile function indices
deteriorate. Doppler interrogation demonstrates a distinctive diastolic flow pattern in the pulmonary artery,
suggestive of PDA. Color flow imaging clearly demonstrates the PDA.

Venous hum
The murmur of venous hum is also a continuous murmur; but is not due to blood flow from high pressure
to low pressure cardiovascular structures (described above). It is best auscultated in the infraclavicular area,
supraclavicular fossa, and at either LUSB or RUSBs. The murmur is very soft and is usually no louder than
grade II/VI. The diastolic part of the murmur is a little bit louder than the systolic portion. The murmur is
heard better when the patient is sitting up. The murmur fully goes away or turns out to be only systolic by
compressing the veins in the neck or by rotating the patient’s head to the opposite side. The most important
feature is that the murmur goes away completely in the supine position. This murmur is the most frequent
of all functional heart murmurs; however, it is not frequently identified by an uninitiated auscultator. The
murmur of venous hum is different from that of PDA in that it is much softer and disappears in the supine
position. The other findings in cardiac evaluation are completely normal. Also, the results of the ECG, chest
X-ray, if performed, are normal, as are the results of the echocardiogram.

Surgically created aorto-pulmonary shunts
A number of aorta-to-pulmonary artery shunts are created by surgery in order to augment pulmonary
blood flow. All these shunt procedures exhibit continuous murmurs on auscultation. In the 1940s,
anastomosis of the subclavian artery to the pulmonary artery on the same side, now called classical Blalock-
[21]
Taussig (BT) operation was used to increase the pulmonary blood flow. Subsequently, several other types
of surgery have been used to accomplish the same purpose of augmenting the pulmonary blood flow, and
these include Potts anastomosis, Waterston operation, central aorto-pulmonary shunt (directly or with a
Gore-Tex graft), and modified BT shunt. In the modified BT shunt, an inter-position Gore-Tex graft is
[22]
inserted between the subclavian artery and the ipsilateral PA . More recently, Sano shunts [23,24] , connecting
the right ventricular outflow tract to the pulmonary artery with a Gore-Tex graft, have been employed to
perfuse the pulmonary circulation. All the above shunts generate continuous murmurs. In practice,
murmurs resulting from the surgically created shunts are difficult to differentiate from the murmur of PDA,
with the exception that the multiple clicks of PDA are not auscultated in subjects who had surgically created
shunts. Information regarding the surgical history and the site of the surgery scar may be useful in
diagnosing the type of operation producing the continuous murmur.

Children with patent BT shunts will have continuous murmurs at the upper sternal border on the same side
as the scar on the chest. On palpation, the brachial and radial pulses are reduced or not palpable in patients
with classic BT shunts, while those with modified BT shunts will not have such pulse deficiency. However, it
should be noted that classic BT shunts are rarely, if ever, performed at this time. Patients who had Potts and
Waterston shunts will have more centrally located continuous murmurs, have either mid-sternal, left
(Potts), or right (Waterston) thoracotomy scars, but it should be known that these shunts are no longer
performed. The central aorto-pulmonary Gore-Tex graft shunts are typically performed via a mid-
sternotomy approach, and the murmur is more medial in location, and they do not exhibit any pulse deficit.
Finally, the Sano shunts usually have no or less prominent diastolic component. The majority of the patients
who had been palliated with any of the above-described shunts will continue to exhibit cyanosis because the