Evaluation of postural tachycardia syndrome by quantitative dynamic colour Doppler sonography with the PixelFlux technique

This patient with hypermobile Ehlers-Danlos syndrome was unable to stand for more than 10 minutes without developing pre-syncope (dizziness, near fainting, blackout).

She was diagnosed with postural tachycardia syndrome (POTS) due to dysautonomia.

With dynamic functional and quantitative color Doppler sonography including PixelFlux measurement of the kidneys, the true nature of the disease was clearly described.

The patient experienced a massive and sudden drop in left ventricular filling by 74% (!) within 3 minutes of getting up. After 5 minutes she had to sit down in order not to lose consciousness.

The table shows that postural tachycardia is not a dysautonomia, but a helpful, albeit – in symptomatic patients – insufficient compensatory mechanism of the body to prevent even worse cerebral perfusion.

Maintaining adequate cerebral blood flow is of critical importance. Loss of cortical brain function, i.e. consciousness, would place the organism in a life-threatening state of immobility and deprive it of the ability to react to threatening external influences.

The filling of the left ventricle can be calculated as the aortic flow volume divided by the heart rate. The values given here refer only to the part of the aortic flow volume below the diaphragm – however, the relative changes accurately characterize the hemodynamic changes.

This image shows the measurement of the aortic flow volume (4200 mL/min) in supine position.

This image shows the sharp reduction in aortic flow volume after only 3 minutes in the standing position with a drop to only 1747 mL/min. The reduction in flow velocity from 125 cm/s in the supine position to 75.5 cm/s in the standing position is impressive (-39 %) .

This diagram precisely describes the organ malperfusion in POTS with a significant perfusion drop of both kidneys.

The only way for the organism to maintain life-saving cerebral perfusion is to increase the heart rate from 75/min to 121/min, an increase of 61% – the hallmark of postural tachycardia syndrome.

The reduced filling of the aorta leads to a partial collapse of the vessel with a reduction in its perfused cross-sectional area from 2.34 cm² to 1.67 cm² – a loss of 29%.

With such a measurement technique, the extent to which the patient is affected by venous pooling in the lower half of the body due to the combination of venous compression syndromes can be accurately described.

V _{(aortic flow volume)} = A _{(aortic transsectional area)} * v _{( aortic flow velocity)}

L _{(Perfusion loss)} = 1-(Δ A * Δ v)

In the actual patient

L =1-( (1,67 cm²/ 2,32 cm²)* (75 cm/s / 125 cm/s) )

L = 1-(0,7198 * 0,608) = 0,56236

This patient loses 56% of aortic flow volume while standing (the ultrasound machine calculated 58% with more data).

In a study of patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and orthostatic intolerance in daily life, a 27% reduction in cerebral blood flow was demonstrated in severely ill patients during a 20° tilt test only (standing upright corresponds to a 90° tilt angle).

In healthy controls, the reduction in cerebral blood flow during a 30-minute 70° tilt test was only 7%.

In the same study, patients with POTS and ME/CFS experienced a 29% decrease in cerebral blood flow. There was also a linear correlation between the sum of orthostatic intolerance symptoms and the degree of CBF reduction at mid-tilt (P < .0005).

Thus, the patient described here has an extreme drop in perfusion that can be accurately quantified by functional color Doppler sonography.

Many patients with POTS are treated with beta-blockers because it is assumed that an inherently disturbed autonomic activity with increased and excessive sympathetic activity as the cause of POTS must be suppressed. It is therefore not surprising that patients in whom a massive orthostatic venous pooling in the lower half of the body due to blocked recirculation to the heart as a result of the combination of compression of the left renal vein, left iliac vein and vena cava as the source of their tachycardia often do not benefit from such treatment. This is because beta-blockers reduce the body’s helpful counter-reaction, the increase in heart rate. Thus the somewhat curious observation delivered in the medical literature is that: ” Some studies have found that low doses of propranolol are superior to higher doses in the treatment of POTS adult patients.”

As a result, in addition to the reduced circulatory volume, cerebral blood flow is also drastically reduced whcih explains the only apparently paradox reaction of many patients which do not tolerate such a treatment.

The proper treatment is an elimination of the excessive venous pooling by deblocking the compressed left renal , left common iliac vein and vena cava inferior.