Pulmonary thromboendarterectomy
Encyclopedia
In thoracic surgery
, a pulmonary thromboendarterectomy, PTE, is an operation
that removes organized clotted blood
(thrombus
) from the pulmonary arteries
.
induced by recurrent/chronic pulmonary emboli).
and full cardiac arrest, with the critical procedure carried out in a standstill operation
.. The reason for the complexity of procedure comes from the anatomy. The obvious part is that a pulmonary bypass is required. Surgeons cannot operate on something they cannot see; the blood going to the lungs has to be diverted from the pulmonary vasculature and lung function taken care of by a machine. Less obvious is that hypothermia is required. This goes back to the pathophysiology of emboli; they are organized, somewhat delicate, essentially part of the vessel wall, and hard to remove completely, unlike in an acute pulmonary embolectomy (for acute pulmonary embolism, which is done without hypothermia). Making this task more difficult is the anatomy of the lung and pathophysiology of chronic thromboembolic pulmonary hypertension (CTEPH); lungs also get blood from the bronchial arteries are often enlarged. The practical implication is that a conventional cardiopulmonary bypass (CPB) is not sufficient to do the surgery because
The solution is a full cardiac arrest, which can be done with hypothermia. So, after going on to CPB and they induce a deep hypothermia (18-20 degrees Celsius), to preserve the patient's brain. Once the patient is cooled off sufficiently the CPB machine is turned off and the surgeon has time to do the delicate work, which takes about 40 minutes, and consists of carefully removing the organized thrombus. The most challenging part of the surgery is finding the optimal plane to dissect the pulmonary artery
. If the surgeon dissects too deeply into the vessel wall the pulmonary vessels may rupture. If the surgeon does not dissect deep enough the clot breaks proximally during extraction and the distal part of the pulmonary vasculture will not have its pulmonary blood flow restored. The right lung is typically done first as it is easier. Video cameras (angioscopes) are used to see deeper into the pulmonary vasculture. At the end an almost beautiful negative of the pulmonary arteries exists—as the emboli over time fill the larger vessels that feed the smaller occluded vessel.. It is not uncommon that collectively this negative almost represents the whole pulmonary tree—the only part missing being what the person was living off before the surgery. Bypass time is typically 345 minutes.
, at places where thrombi were removed, [Levinson et al., 1986] and thus have less than ideal oxygen saturation values. This results because with the thrombus removal the surgeon strips out the pulmonary endothelium. The challenge for the ICU physician thus is getting the extra water out of the lungs, (for which they make use of the strong diuretic furosemide
) to get decent oxygen saturation values, yet maintain the blood pressure. Maintaining these two parameters can be a challenge. Maintaining a good oxygen saturation can be accomplished by run the patient dry (with a diuretic) and set a high BiPAP (bidirectional positive airway pressure). Problem is that a high BiPAP leads to a poor venous return, which means the blood pressure suffers. Adding volume would help with the blood pressure, but would make the edema worse so it is generally avoided. Adding albumin
does not help; the pulmonary arteries are too porous post-operation. So, a balancing act is required between blood pressure and oxygen saturation
that is controlled with the BiPAP and the diuretic
.
. Further, pulmonary vascular resistance usually drops back to close normal levels. Since the pulmonary resistance is proportional to the pressure driving the pulmonary flow (P=Q*R), it follows that the pulmonary pressure decreases. This in turn means that the work per time (power) decreases because it is equal to the pressure gradient times the volumetric flow, which in this case is the cardiac output. As a result of the operation, patients are spared from pulmonary hypertension and further right ventricular hypertrophy
. Most pleasing is that patients who previously had right heart dysfunction often recover function.
's cardiothoracic surgery department is widely recognized as a pioneer in the relatively new surgery, having performed more PTEs than the rest of the world combined (over 2100 since 1970 out of a total of 3500 worldwide) with the lowest mortality rate (less than 5%).
are both operations that removed thrombus from the lung's arterial vasculature. Aside from this similarity they differ in many ways.
Thoracic surgery
Thoracic surgery is the field of medicine involved in the surgical treatment of diseases affecting organs inside the thorax . Generally treatment of conditions of the lungs, chest wall, and diaphragm....
, a pulmonary thromboendarterectomy, PTE, is an operation
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
that removes organized clotted blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
(thrombus
Thrombus
A thrombus , or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system...
) from the pulmonary arteries
Pulmonary artery
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....
.
Indication
PTE is a treatment for chronic thromboembolic pulmonary hypertension (pulmonary hypertensionPulmonary hypertension
In medicine, pulmonary hypertension is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion...
induced by recurrent/chronic pulmonary emboli).
Description of the surgery
A PTE has significant risk; mortality for the operation is typically 5%. PTEs are risky because of what is done and how it is done. PTEs involve a full cardiopulmonary bypass (CPB), deep hypothermiaHypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
and full cardiac arrest, with the critical procedure carried out in a standstill operation
Standstill operation
Standstill operation is a surgical procedure that involves cooling the body of the patient and stopping blood circulation. It is used to repair brain aneurysms and aortic arch defects....
.. The reason for the complexity of procedure comes from the anatomy. The obvious part is that a pulmonary bypass is required. Surgeons cannot operate on something they cannot see; the blood going to the lungs has to be diverted from the pulmonary vasculature and lung function taken care of by a machine. Less obvious is that hypothermia is required. This goes back to the pathophysiology of emboli; they are organized, somewhat delicate, essentially part of the vessel wall, and hard to remove completely, unlike in an acute pulmonary embolectomy (for acute pulmonary embolism, which is done without hypothermia). Making this task more difficult is the anatomy of the lung and pathophysiology of chronic thromboembolic pulmonary hypertension (CTEPH); lungs also get blood from the bronchial arteries are often enlarged. The practical implication is that a conventional cardiopulmonary bypass (CPB) is not sufficient to do the surgery because
- too much blood would be in the surgical field and
- the delicate thrombi would be difficult to remove completely.
The solution is a full cardiac arrest, which can be done with hypothermia. So, after going on to CPB and they induce a deep hypothermia (18-20 degrees Celsius), to preserve the patient's brain. Once the patient is cooled off sufficiently the CPB machine is turned off and the surgeon has time to do the delicate work, which takes about 40 minutes, and consists of carefully removing the organized thrombus. The most challenging part of the surgery is finding the optimal plane to dissect the pulmonary artery
Pulmonary artery
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries that carry deoxygenated blood....
. If the surgeon dissects too deeply into the vessel wall the pulmonary vessels may rupture. If the surgeon does not dissect deep enough the clot breaks proximally during extraction and the distal part of the pulmonary vasculture will not have its pulmonary blood flow restored. The right lung is typically done first as it is easier. Video cameras (angioscopes) are used to see deeper into the pulmonary vasculture. At the end an almost beautiful negative of the pulmonary arteries exists—as the emboli over time fill the larger vessels that feed the smaller occluded vessel.. It is not uncommon that collectively this negative almost represents the whole pulmonary tree—the only part missing being what the person was living off before the surgery. Bypass time is typically 345 minutes.
Recovery/ICU
The ICU recovery involves several challenges. Most patients get significant reperfusion pulmonary edemaPulmonary edema
Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
, at places where thrombi were removed, [Levinson et al., 1986] and thus have less than ideal oxygen saturation values. This results because with the thrombus removal the surgeon strips out the pulmonary endothelium. The challenge for the ICU physician thus is getting the extra water out of the lungs, (for which they make use of the strong diuretic furosemide
Furosemide
Furosemide or frusemide is a loop diuretic used in the treatment of congestive heart failure and edema. It is most commonly marketed by Sanofi-Aventis under the brand name Lasix...
) to get decent oxygen saturation values, yet maintain the blood pressure. Maintaining these two parameters can be a challenge. Maintaining a good oxygen saturation can be accomplished by run the patient dry (with a diuretic) and set a high BiPAP (bidirectional positive airway pressure). Problem is that a high BiPAP leads to a poor venous return, which means the blood pressure suffers. Adding volume would help with the blood pressure, but would make the edema worse so it is generally avoided. Adding albumin
Human serum albumin
Human serum albumin is the most abundant protein in human blood plasma. It is produced in the liver. Albumin constitutes about half of the blood serum protein...
does not help; the pulmonary arteries are too porous post-operation. So, a balancing act is required between blood pressure and oxygen saturation
Oxygen saturation
Oxygen saturation or dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.It has particular significance in medicine and...
that is controlled with the BiPAP and the diuretic
Diuretic
A diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...
.
Post-surgery
The benefits of PTEs are significant. Most patients after surgery no longer suffer from shortness of breath and therefore have a much improved quality of lifeQuality of life
The term quality of life is used to evaluate the general well-being of individuals and societies. The term is used in a wide range of contexts, including the fields of international development, healthcare, and politics. Quality of life should not be confused with the concept of standard of...
. Further, pulmonary vascular resistance usually drops back to close normal levels. Since the pulmonary resistance is proportional to the pressure driving the pulmonary flow (P=Q*R), it follows that the pulmonary pressure decreases. This in turn means that the work per time (power) decreases because it is equal to the pressure gradient times the volumetric flow, which in this case is the cardiac output. As a result of the operation, patients are spared from pulmonary hypertension and further right ventricular hypertrophy
Right ventricular hypertrophy
Right ventricular hypertrophy is a form of ventricular hypertrophy affecting the right ventricle.Blood travels through the right ventricle to the lungs via the pulmonary arteries. If conditions occur which decrease pulmonary circulation, meaning blood does not flow well from the heart to the...
. Most pleasing is that patients who previously had right heart dysfunction often recover function.
History and development
The UCSD Medical CenterUCSD Medical Center
UC San Diego Health System is an academic health system in San Diego and has been in operation since 1966. It is composed of UC San Diego Medical Center, Thornton Hospital, Moores Cancer Center, Shiley Eye Center, Sulpizio Cardiovascular Center and Jacobs Medical Center , as well as other primary...
's cardiothoracic surgery department is widely recognized as a pioneer in the relatively new surgery, having performed more PTEs than the rest of the world combined (over 2100 since 1970 out of a total of 3500 worldwide) with the lowest mortality rate (less than 5%).
Relation to pulmonary thrombectomies
PTEs and pulmonary thrombectomiesPulmonary thrombectomy
In thoracic surgery, a pulmonary thrombectomy, is an emergency procedure that removes clotted blood from the pulmonary arteries.Mechanical thrombectomies can be surgical or percutaneous ....
are both operations that removed thrombus from the lung's arterial vasculature. Aside from this similarity they differ in many ways.
- PTEs are done non-emergently whilst pulmonary thrombectomies are typically done as an emergency procedure.
- PTEs typically are done using hypothermia and full cardiac arrest.
- PTEs are done for chronic pulmonary embolism, thrombectomies for severe acute pulmonary embolism.
- PTEs are generally considered a very effective treatment, surgical thrombectomies are an area of some controversy and their effectiveness a matter of some debate in the medical community.
External links
- UCSD Pulmonary Thromboendarterectomy Program - UC San Diego Medical Center
- A Patient Guide to PTE - Ottawa Heart Institute.
- Pulmonary Thromboendarterectomy - Mayo ClinicMayo ClinicMayo Clinic is a not-for-profit medical practice and medical research group specializing in treating difficult patients . Patients are referred to Mayo Clinic from across the U.S. and the world, and it is known for innovative and effective treatments. Mayo Clinic is known for being at the top of...