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Rao. Vessel Plus 2022;6:22 https://dx.doi.org/10.20517/2574-1209.2021.105 Page 19 of 24

Table 8. Etiology of presystolic murmurs. Reproduced from Rao [5]

Mitral stenosis, rheumatic and congenital
Tricuspid stenosis, congenital and rheumatic
Left (or right) atrial myxoma

is an atrial defect decompressing the right atrium, the mentioned abnormalities are not present.

ECG shows right atrial enlargement. M-mode echo demonstrates reduced amplitude of the tricuspid valve
leaflets. 2D echo may show a small tricuspid valve opening. Doppler interrogation of the RV inflow region,
measuring tricuspid inflow gradient, is useful in quantifying the gradient across the tricuspid valve.

Atrial myxoma
Atrial myxomas are infrequent in the pediatric population. If present, atrial myxomas are more common in
the left than in the right atrium. Embolic episodes or postural induced syncopal episodes are likely to be the
presenting symptoms. Presystolic murmurs indicative of mitral valve stenosis, which varies with patient
position, are suggestive of myxoma. 2D echo is an excellent method in detecting myxoma.

Continuous murmurs
By definition, murmurs that start in systole and spill into diastole are named continuous murmurs. The
systolic component of the murmur crescendos up to the 2nd heart sound whilst the diastolic part
decrescendos to a variable time into the diastole (Figure 5; top).

The continuous murmurs are typically caused by blood flow from cardiac chambers or blood vessels with
high pressure/resistance into venous structures with lower pressure/resistance. The blood flow occurs both
during systole and diastole since there is a pressure/resistance difference during the entire cardiac cycle. The
continuous murmur must be differentiated from the to-and-fro murmur (Figure 5; bottom). The latter is a
mixture of systolic ejection murmur (due to aortic or pulmonary stenosis) and an early diastolic
decrescendo murmur (due to aortic or pulmonary regurgitation). A distinct gap between the ejection
systolic murmur and the 2nd heart sound is seen in to-and-fro murmurs (Figure 5; bottom), whereas such a
gap is not seen in the continuous murmur (Figure 5; top). The etiology of continuous murmurs is shown in
[Table 9]. The murmur location, changes in the murmur character with changes in body posture, and
findings in history and physical examination of the primary cardiac defect are useful in the differential
diagnosis.

Patent ductus arteriosus
The continuous murmur associated with PDA is better auscultated at the LUSB. The murmur varies from
grades I to V/VI in loudness. The PDA is a frequent cause of pathologic continuous murmur.
Characteristically, numerous ejection clicks within the murmur are auscultated and are considered typical
for PDA. The murmur is also portrayed as a machinery murmur. Most of the time, there is no change in
murmur characteristics with a change in the body position, though the diastolic part of the murmur is
auscultated better when the patient is supine than when he/she is in an upright position. Nevertheless, in
patients with extremely small PDAs, the continuous murmur may either disappear or become only systolic
in timing in sitting-up position, but resumes to continuous type following resumption of supine posture .
[1]
The suggested reason for this phenomenon is “kinking” of the ductus when the patient is in the upright
position . The LV impulse is within normal limits in small PDAs, but it is prominent in patients who have
[1]
moderate to large PDAs. A thrill is usually appreciated at the upper left sternal border and/or in the
suprasternal notch. The 2nd sound is frequently within normal range; however, it is hard to be heard since