Blood flow in the veins - importance for the circulation often underestimated

Your blood, after reaching the body tissues from the left heart via the arteries, must return to the right heart. This is the only way to maintain a healthy and efficient circulation. Your leg muscles, the muscles of the pelvic floor and trunk, the diaphragm and the heart are all important for this. In other words, what the heart essentially does alone for the arterial circulation is taken over by various muscle groups for the venous return flow.

The importance of venous return is underestimated by most people, including physicians.

Blood flow in the veins - important for healthy circulation

In contrast to the arterial inflow from the heart to the various organs, the venous return flow is a more complex process and therefore also one that is more prone to disruption. Especially when you are supposedly standing still, the return of venous blood to the heart against the force of gravity is a great challenge to your body. Consider that the distance from the big toe to the right part of the heart is about 4/7 of your body length. So it's a decent uphill climb against gravity.

The aim of venous return is to offer the right heart enough blood volume to pump so that the oxygen-depleted venous blood can be passed on to the lungs to be re-oxygenated. If this does not succeed in sufficient form, then adrenaline-mediated compensatory mechanisms kick in.

Symptoms of venous circulatory disorders - palpitations, lightheadedness, swaying, trembling, fainting.

Subjective symptoms of disturbed venous return are lightheadedness occur when standing up, after standing for a long time and also when walking slowly.

• inner restlessness
• fast heartbeat
• rapid fatigability
• Drowsiness
• Powerlessness

Fainting rarely occurs. If you pay close attention, you may observe unconscious compensatory reactions in your fellow human beings to improve venous return and thus prevent fainting. When standing, there is a tendency to sit down quickly, to sway or, in rare cases, a clearly visible muscle tremor.

Since circulatory disorders are accompanied by sometimes considerable adrenaline-mediated activation, there is a risk of anxiety reactions in connection with standing or accompanying events. Consequently, a somato-psychic circulatory disorder may develop into a psycho-somatic disorder with anxiety up to fixation in the form of a phobia.

Now, to better understand these processes we need to look at the different muscle pumps of venous return.

Blood flow in the veins - different muscle pumps

So how can venous blood flow uphill while standing?

In order for venous return to function and for enough blood to be available to the heart again, various muscle pumps must function and interact properly.

Once the oxygen-rich blood has reached your big toe via arteries and delivered enough oxygen to the tissues, it must now return to the heart. This happens via the veins. Now, there is no heart in the big toe to pump the blood up against gravity, so there are other pumps at work here. The venous return begins with the peripheral muscle pump.

Peripheral muscle pump - from the big toe to the groin

The peripheral muscle pump of the legs compresses the leg veins so that blood is pushed toward the heart. Compared to arteries, veins are much weaker in muscle and thinner in wall (leg artery approx. 1.0-1.5 mm vs. leg vein approx. 0.5-0.75 mm) and can therefore be easily compressed. Even when you are supposedly standing still, you keep involuntarily tensing your legs by making slight movements. This serves to support venous return.

The return of the blood with the force of gravity towards the feet is prevented by check valves, the venous valves. These are found almost exclusively in the extremities, i.e. the legs and the arms. Seen from the legs, from the groin and thus from the transition to the pelvic-abdominal area, there are no more venous valves that prevent the backslide of blood footward.

Pelvic floor muscle pump - the heart in your pants

The pelvic floor is a complex structure of very different muscles. These contract involuntarily, i.e. unconsciously: Tension in inhalation, relaxation in exhalation. In the process, the rich venous plexus of the pelvis is squeezed out and pressed towards the heart; the pelvic floor is, so to speak, the heart in the pants.

If you have ever done a pelvic floor workout, you will have noticed that as the pelvic floor tightens, the muscles on the inside of the thigh also tighten. Thus, the femoral veins are expressed toward the abdomen and thus toward the heart.

The weaker the pelvic floor muscles, the less the pelvic floor contributes to circulation and the venous blood then pools in the pelvic veins. You can imagine it like this, a slim Bordeaux bottle becomes a bulbous Bocksbeutel bottle.

This increased blood volume also increases the pressure in the venous plexus of the pelvic floor, making it harder for blood to drain from the legs. Leg edema is often the result here. In addition, your pelvic floor has numerous other functions.

Body trunk muscle pump - good basic tension important

The muscles of the trunk keep tension on the abdominal veins. This is especially important because abdominal veins do not have venous valves, except in isolated cases. You can imagine it as if you want to squeeze a half-full upright shampoo bottle upwards; the opening represents the transition to the right ventricle of the heart. If you don't build up tension with your hands, then you won't be able to squeeze the bottle. In other words, the venous blood has a harder time getting back to the right heart if there is too little body tension.

Lung muscle pump - strong diaphragm especially important

From the middle of the abdomen, the suction force of the lungs (and heart) begin to support the return flow. As you inhale, the diaphragm descends toward the abdomen and your lungs expand. This creates a negative pressure in the lungs, which exerts suction on venous blood in the abdomen. This happens 12-16 times per minute, depending on the number of breaths.

If your diaphragm is too weak, then venous return is reduced and your performance is impaired. A weakened diaphragm often occurs as a result of shallow mouth-to-chest breathing. The diaphragm is simply not exercised enough in this way; this is just as much a deconditioning as we know from other muscles in the body. Especially in older people, who usually eat less meat, there is also a vitamin B12 or iron deficiency. We can measure lung muscle strength well at Cardiopraxis using manometry.

Cardiac muscle pump - suction during ejection phase

When you feel your pulse, the main chambers eject blood toward the lungs or the systemic circulation. At the same time, the heart moves toward the apex. With the upstream connecting valves closed - tricuspid valve on the right, mitral valve on the left - this exerts a suction on the respective atrium and the upstream venous system via a negative pressure. On the side of the right main chamber, this promotes the return flow from the systemic circulation.

The deflection of the main chamber in the direction of the cardiac apex, and thus also indirectly the suction force, can be measured well in cardiac ultrasound with the so-called tissue Doppler. It is 3.0 - 3.5 cm in the integral per cardiac action for the lateral wall of the right main chamber, and 2.0 - 2.5 cm for the left main chamber. If the value on the right side is lowered, e.g. almost always after heart surgery and/or by taking e.g. a beta-blocker, then there is an inflow congestion into the chest cavity. We can recognize this in the ultrasound alone by a widening of the large lower body vein, the inferior vena cava, of significantly more than 15 mm when standing.

In addition to the suction force, the frequency of the process also plays a role, of course. If your heart rate is below 50 bpm, then a so-called bradycardic heart failure can occur due to a too low heartbeat.

The interaction of all muscle pumps

For orderly forward flow in a hydraulic system, the pressure in the upstream system must be higher than in the downstream system. We call this pressure gradient. In the case of venous return, this is best explained starting from respiration.

Inhalation. When you inhale, the diaphragm tenses toward the abdomen and the lungs expand. As the pulmonary arteries dilate, the vascular space expands significantly and the pressure drops. As the diaphragm pushes downward, the organs in the abdominal cavity are compressed, and with them the thin-walled veins. Thus, the pressure increases here. The result is an increase in the pressure gradient between the abdominal cavity (increase) and the thoracic cavity (decrease). Consequently, more venous blood flows from the abdominal to the thoracic cavity.

Exhalation. When you exhale, the diaphragm relaxes towards the chest cavity and the lungs contract due to their elastic properties. Consequently, the pulmonary arteries also become narrower and the pressure increases. At the same time, the pressure in the abdominal cavity decreases. The pressure gradient between the abdominal and thoracic cavities becomes smaller, resulting in reduced forward flow toward the heart.

In order to counteract a footward backflow here, the pelvic floor muscles tense during exhalation and the pressure in the pelvis increases. A pressure gradient is thus created between the pelvic cavity and the abdominal cavity, so that blood can flow in the direction of the abdominal cavity. At the same time, as the pelvic floor tightens, the muscles of the inner thigh also tighten. The result is that venous blood can flow from the thigh into the abdominal cavity (past the pelvis).

Heart and legs. Independently of respiration, a pressure gradient into the upstream and downstream compartments is also maintained by cardiac action and involuntary movement of the legs to support forward blood flow. Backflow into the legs is prevented at all times by the venous valves.

Circulatory training for the veins

If you train the venous return, then you improve your performance and your condition. Basically, all approaches that focus on the trunk of the body are suitable. Yoga is excellent here because, in addition to the muscles of the trunk of the body, the pelvic floor and diaphragm are also strengthened.

Sometimes a specific physiotherapeutically guided pelvic floor training is necessary to learn the response, i.e. the feeling for the pelvic floor. Only when the pelvic floor has been professionally trained, then training with vibration plates, e.g. Power-Plate or Galileo, also makes sense.

 Cardiopraxis - Cardiologists in Düsseldorf & Meerbusch