The Failure Analysis of LVAD (Left Ventricular Assist Device)

The LVADs (or left ventricular support devices) are becoming a more viable treatment as an option for heart failure, either as a DT (permanent designation) therapy or a BTT (bridge to heart transplantation). The authors of [13] contend in their report that the former is becoming more common in recent years, owing to a lack of donated organs and an increase in patients who are elderly and unfit for heart donation. However, significant advancements in LVAD technology continue to increase both the long-term efficiency and results of life [14]. Moreover, it also includes the CF-LVADs (continuous-flow devices) emergence that are more durable and also smaller than the older pulsatile models.

Figure 1: A clear illustration of the left ventricular assist devices

In fact, the increase in the average duration of the mechanical long-term’s support makes the durability of the device (as measured by the device’s rate of failure over a given period) to become an increasing core contributor for the survival of patients, overall life’s quality, and morbidity [7]. Note that the failure of the device can be fatal in the most severe cases. However, the subsequent requirement for the replacement of pumps, in other circumstances, may incur additional costs of healthcare. According to authors in [20], such scenario may also result in the exposure of the patients to potentially complications that are very serious such as bleeding and thrombosis [1]. Despite some remarkable improvements in the CF-LVADs’ durability, continuing device failure’s causes involves the mechanical problems like the percutaneous lead damage and the drive unit failure, as well as other conditions such as device hemolysis, thrombosis, and other related infections.

Figure 2: All the component of the left ventricular assist devices and the way they are arranged.

For this reason, the current systematic review mainly aims at assessing the present CF-LVADs’ long-term durability as defined by both the death that relates to the failure of the pump and the rates of the device exchange, and also the evaluation of the some of the major causes of the failure of the device [19]. In this case, some of the secondary endpoints require long-term survival without replacing the device. In their article, authors in [12] notes that the Heart transplant acts as the optimal treatment for the patients having advanced failure of the heart. However, the option is mainly dependent on the donor hearts’ supply [3]. In such a case, the use of various medical interventions becomes significant for the individuals that awaits a donor organ. Authors in [18] states that the medical interventions include intravenous inotropes. Other alternative strategies of treatment, that in most cases referred to as BTT (bridge to transplant, is for surgical implantation of a left ventricular assist device.

The Meaning of LVAD

An LVAD refers to a mechanical pump that helps in supporting a left ventricle function up to the time the heart of donor becomes available. In this paper, the causes of the failure of the LVAD are discussed [3]. Moreover, effects and the way of fixing each of such causes of the failure of LVAD are also discussed. In general, the LVADs (or the left ventricular assist devices) have resulted in the revolutionary of the treatment of the heart failure that is advanced, but failure remains a substantial risk. According to authors in [17], this mechanical pump is implanted in the inside the chest of a person for helping a weakened heart pump blood. In their research, the authors in [14], notes that the LVAD does not replace the heart, unlike the total artificial heart. In other words, the LVAD just helps the heart in doing its job [16]. In general, it means death and life for a person waiting for heart transplant or a person whose heart is in need of some rest after open-heart surgery [5]. For this reason, the LVAD is mostly referred to as the bridge to transplant.

Additionally, LVADs can also be useful as a destination therapy [2]. In other words, it is used in some long-term in terminally ill people having the condition of making it impossible for the patients to get the transplant of heart [15]. In fact, the left ventricular assist devices are revolutionizing the advanced heart failure treatment.

Figure 3: LVAD. (Source: The article by the authors in [6])

The Principle Working of an LVAD

The researchers in [13], notes that the LVAD is a pump just like the heart. Moreover, it is surgically implanted below the heart just below the heart. In this case, the one end of the LVAD is attached to the chamber of the heart (the left ventricle) that helps in pumping blood into the body and out of the heart. In their research, the writers in [14], argue that the other end of the LVAD is attached to the main artery of the body, the aorta. Blood is made to flow from the heart into the pump. Subsequently, the blood is then moved into the aorta when the sensors indicate that the left ventricular assist device is full. According to the researchers in [7], a tube from the left ventricular device is also made to pass through the skin. Such a tube is known as the driveline and it is used for connecting the pump to the external controller and the source of power.

In general, both the pump in addition to its connections are implanted at the time of the open-heart surgery [8]. However, a power pack, a computer controller, and a reserve pack are left outside the body. Note that some models allow the person to wear such external units on either a harness outside or a belt [4]. This power pack must also be recharged at night. In most cases, the LVAD is helpful in restoring the flow of blood to a person whose heart has been weakened by some diseases of the heart [11]. Such a process helps in relieving various symptoms, such as short breath or being constantly tired. In rare cases, the LVAD allows the heart to recover its normal ability because it can give the heart a chance to rest [9]. Further, it either improves or maintains other organs, lets the person go through the rehabilitation of cardiac, and helping with doing exercise. According to the authors in [12], there are several risks and failures involved with any surgery.

Figure 4: Sample image of LVAD. (Source: Article of the authors in [11])

Causes of LVAD Failure or Risks

Some of the risk or failures associated with LVADs include device failure, infection, blood clots, internal bleeding, kidney failure, stroke, and the respiratory failure [10]. In general, the DLIs (or the LVAD driveline infections) acts as one of the most common type of LVAD-associated infection [11]. People have expanded their understanding of the DLI epidemiology in the past decades. As a result, there is a standardization of the definition of the LVADIs, the investigated potential of the new modalities for the Diagnosis of the DLI, and the improved rates of infection through the changes in the techniques of implantation [1]. Such failures or challenges include improving or standardizing both the targeted and the empiric antimicrobial therapy, defining the population of the patients that benefits from the exchange of the device and transplant, and the expansion of the human understanding of effective driveline site of exit topical therapies and dressings [2]. Moreover, in this era of antibiotic resistance expansion, people need to continue investigating novel, the non-antibiotic therapies that are helpful for treating and also preventing the DLIs.

Figure 5: How the LVAD is installed in the body of human being. (Source: An article published by the authors in [7]).

As noted earlier, the emergence of the left ventricular assist devices has been very essential in field of health [12]. Again, the key advances in the technology of LVAD continues to improve both the long-term quality and outcomes of life. The study done by [4] and [5] reveals that it also includes the CF-LVADs (continuous-flow devices) emergence that are more durable and also smaller than the older pulsatile models. In their article, the researcher in [3], notes that the increase in the average duration of the mechanical long-term’s support makes the durability of the device (as measured by the device’s rate of failure over a given period of time) to become an increasingly core contributor for the survival of patients, overall life’s quality, and morbidity. Note that the failure of the device can be fatal in the most severe cases. According the authors in [14], the subsequent requirement for the replacement of pumps, in other circumstances, may incur additional costs of healthcare. The scholars in [4], notes that such scenario may also result in the exposure of the patients to potentially complications that are very serious such as bleeding and thrombosis.

Despite some remarkable improvements in the CF-LVADs’ durability, continuing device failure’s causes involves the mechanical problems like the percutaneous lead damage and the drive unit failure, as well as other conditions such as device hemolysis, thrombosis, and other related infections [6]. For this reason, the current systematic review mainly aims at assessing the present CF-LVADs’ long-term durability as defined by both the death that relates to the failure of pump and the rates of the device exchange, and also the evaluation of the some of the major causes of the failure of the device [15]. In this case, some of the secondary endpoints require long-term survival without replacing the device. Heart transplant acts as the optimal treatment for the patients having advanced failure of the heart, however, the option is mainly dependent on the donor hearts’ supply. In such a case, the use of various medical interventions becomes significant for the individuals that awaits a donor organ. Researchers in [16] note that the medical interventions include intravenous inotropes. Other alternative strategy of treatment, that in most cases referred to as BTT (bridge to transplant, is for surgical implantation of a left ventricular assist device.

LVADs (or the left ventricular assist devices) are revolutionizing the treatment of the failure of the heart [18]. Despite the continued rapid advancement of the technology of LVAD, all the current devices are still in need of the external source of power with the supplied energy through tunneled percutaneous driveline [4]. In general, the DLIs or the driveline infections are the most common type of the LVAD infection [8]. The frequent occurrence of the driveline infections results from the creation of the conduit for entry of both the prosthetic material and the bacteria at the exit sites of the driveline [7]. As result, there is also the formation of the bacterial biofilms that in most cases contribute to the failure of the device [1]. The GIB (or the gastrointestinal bleeding) along with the DLI and stroke, are some of the leading causes of the failure due to the unplanned readmission for the patients with LVADs. Writers such as [9] and [19] notes that that the cost of readmission for the medium hospital is more than 7,000 US dollars.

Figure 6: How the LVAD Works

The complications and the prevalence of the LVAD, that includes the infections, are increasing because of the expansion of the use of the LVADs from short term use as BTT (bridge to transmission) for also including the long-term DT (destination therapy) in patients who do not qualify for the transplant. A writer in [1], notes that various retrospective studies and several recent reviews have outlined the broad treatment and the epidemiology approach for the LVADLs.

Definition of the Failures and the Rate of Infection

There was a proposal of consensus guidelines to help in defining the LVADIs by the ISHLT in 2011. Within such definition, the LVAD DLIs is divided into superficial and deep infections. According to the author in [1], the infections involve the soft tissue that surrounds the exit site of the driveline and are also accompanied by the erythema, purulent drainage, and the increase in temperature around the site. The writers in [20], clearly illustrates that the deep infections also include the muscular and the fascia layers. Often, the exact extent of the infection can only be determined at the time of the exploration of the surgical, the distinction between the deep and the superficial infection is of limited utility in the care of clinics [19]. Moreover, the differentiation of the DLI from the infection of the pump packet, which is the infection, involves the cavity of the body that holds the LVAD pump, and it can also be tough when the surgical investigation misses.

Rates of Infection

Both the prevalence and the incidence of the DLIs shows great variations between studies depending on the definition used and the population evaluated [2], [19], and [3]. Most recently, the studies have attempted to go beyond the rates of incidence and the risk evaluation for the DLI and the age. Evidently, there is no appearance of the advanced age to be one of the risk factors for DLI [3]. Moreover, some of the recent factors shows no difference in the rate of infection in patients under and over 65 years of age. In the article written by the authors in [20], [9], [13] and [14], it is indicating that such findings were mostly related to the high rate of activity, and therefore increased the trauma of the driveline exit site risk in the younger population. Authors in [4], further explain that the trauma has been associated with the risk factor for the subsequent DLI.

Diagnosis

Usually, the diagnosis of the DLI takes place when the caregiver, the patient, or the provider notes the warmth, erythema, or the purulent drainage around the exit site of the driveline. However, there is a difficulty in the determination of whether the infection is limited to the exit site of the driveline or involves the deeper structures [5]. Note that there are no particular guidelines involves in using the imaging for assessing the infection’s extent after the diagnosis of a DLI. Although the ultrasound can be helpful in detecting the fluid packets, it otherwise gives very little information regarding the whether there is an infection of the structures [18]. Furthermore, there is a limited utility that is given the artifact caused by the device in the CT (or the computer tomography)

As a result of the limitations of the techniques of the standard imaging, there has been a consideration for the evaluation of DLIs for more advanced imaging options. In some research, it was concluded that the emission of the gallium single photon tomography (the SPECT - CT) may result in the elucidation of the extent of the structure of the LVAD that are involved after the diagnosis of the DLI. In effect, it can result in the inform decisions that relates to the need for the exchange of device [7]. However, it should be noted that some publications are questioning the sensitivity of such modality of imaging since inflamed but the tissue without infection might be misidentified as one of the infections [16]. The PET or the position emission tomography – CT is also undergoing investigation as one of the modality of imaging for the LADI. Moreover, it has become very useful in the identification of the LVAD components infection and the response to the therapy. PET – CT may also be significant in revealing some of the unsuspected distant sites of the infection like the paravertebral abscess [8]. Often, given the prolonged bacteremia that in most cases accompanies the DLIs, particularly with the pathogens such as the pseudomonas aeruginosa or the Staphylococcus aureus, the evaluation for the metastatic infection sites can be vital.

Pathogens

In cases of the LVAD DLI, the pathogens involved are predominantly the organisms of the skin, that includes coagulase negative staphylococci, aureus, and the Corynebacterium spp. Nonetheless, both enterobacteria and the p. aeruginosa are also isolated in many occasions, with the candida found to be less pathogen. In the evaluation of the pump packet infections, the pathogens that are implicated in the local infections, madiastinitis without the infection of the bloodstream, and the infections of the cardiovascular implantable electronic device, it is evident the most common pathogens that are isolated were the Gram-negative rods and the Gram-positive cocci.

As well, the polymicrobial infections are also common, and they may involve the resistant organisms of the multi-drug resistant [20]. Apparently, it is increasingly becoming clear that the polymicrobial infections are in most cases occurs because of the superinfection of an existing driveline site with an infection despite the fact patient remain on suppressive therapy for the initial pathogens. P. aeruginosa is one of the most common secondary pathogens in these cases [8]. Moreover, it is always not easy to distinguish organism of the commensal skin from the true pathogens.

Pathogenesis

In general, the LVAD driveline is useful in providing an ideal surface to form the biofilms because of its high area of surface, and there has also been a good demonstration of the biofilm formation in a staphylococcal DLI’s murine model [10]. Again, there is also a thought of involvement of the biofilms in the DLI’s pathogenesis because of the other organisms of biofilm-formation such as candida spp., p. aeruginosa, and the enterococcus spp.

The occurrence of the biofilms takes place when the bacteria adhere to the surface. In the process, it forms the microcolonies that are embedded in the matrix (or the substance of extracellular polymeric). An actual organism may only account for about 10% of the biofilm’s biomass in such environment [16]. Again, the matrix’s composition varies from species to species. For this reason, it can be used for the protection of the cells of the bacteria from the immune system host and the prevention of the antibiotics’ penetration. According to the authors in [4], such factors contribute to the selection of the antibiotic specifically vital in the DLI’s treatment.

Treatment

In reality, there is no comprehensive guidelines used to treat the LVADIs, even though the general guidelines for the duration of treatment proposed by the surgical debridement or the antimicrobial therapy for DLI. In general, there is no suggestion for the use of suppressive antibiotics for the isolated DLI [19]. However, they should also be taken into consideration if the infection of the pump pocket is suspected. Currently, the guidelines fail to address the choice of targeted antimicrobial or the empiric therapy for the LVAD DLIs.

How to Fix some of the Failures of the LVAD

Fixing these failures involve carrying out various therapies, as noted by authors in [17]. Such therapies include empiric therapy, suppressive therapy, targeted therapy, alternative therapies, and the device exchange.

Empirical Therapy

A culture of the site has to be obtained for any of the suspected DLI. Moreover, an empiric therapy should be started at the time of waiting the results. There should also be an establishment of the best empiric therapy for the DLIs. Often, oracle of antibiotics is used for the early localized infections. But in general, it is described as the inflammation or the drainage around the driveline site of exit without systematic concerns or symptoms for the underlying abscess. At the university of Minnesota, the present and recommended choice of the empiric antibiotic for the early infections is the doxycycline one hundred milligrams for the BID for a period of two weeks [1]. Remember that the choice of the antibiotic is adjusted as the required based on the results of the culture [19]. Either when the systematic symptoms or the for more extensive local infections, patients are admitted to the hospital for imaging, monitoring, and wide-spectrum antibiotics while at the same time waiting for the cultural results.

Targeting Therapy

The empirical antibiotics can always be changed to the targeted therapy after the identification of the pathogens that are responsible for the DLI. Currently, there is an availability of the multiple options and the choice of antibiotic that are guided by the anecdotal success reports rather than the rigorous evidence [3]. Failure to get evidence is specifically perplexing when there is a consideration of rifampin as part of a treatment regimen. By definition, rifampin refers to a bactericidal antibiotic that can eradicate and penetrate the biofilms [3]. With another antibiotic, the rifampin can only be used as an adjunctive therapy because of the potential for the development of the resistance. However, it also demonstrates the synergy with the common antibiotics, that in effect results in the appealing addition to the therapy for the DLIs [20]. Nonetheless, there is an interaction of the warfarin with the rifampin that significantly causes the instability of INR to lead to the complications such as CVA and GIB [18]. Presently, neither the potential treatment nor the bleeding risks benefits of the rifampin have already been studied in patients having the LVADIs. Moreover, there is also an association of the of the problem with other factors.

Conclusion

In summary, there are various failures associated with LVAD (or the left ventricular assist device). Such failures can be very severe that in some cases might results in deaths. However, there are several ways to fix such problems. As already seen, the diagnosis of the DLI takes place when the caregiver, the patient, or the provider notes the warmth, erythema, or the purulent drainage around the exit site of the driveline. However, there is a difficulty in the determination of whether the infection is limited to the exit site of the driveline or involves the deeper structures. Note that there are no particular guidelines involves in using the imaging for assessing the infection’s extent after the diagnosis of a DLI. Although the ultrasound can be helpful in detecting the fluid packets, it otherwise gives very little information regarding the whether there is an infection of the structures. Furthermore, there is a limited utility that are given the artifact caused by the device in the CT (or the computer topography)

As a result of the limitations of the techniques of the standard imaging, there has been a consideration for the evaluation of DLIs for more advanced imaging options. In some research, it was concluded that the emission of the gallium single photon tomography (the SPECT - CT) may result in the elucidation of the extent of the structure of the LVAD that are involved after the diagnosis of the DLI. In effect, it can result in the inform decisions that relates to the need for the exchange of device. However, it should be noted that some publications are questioning the sensitivity of such modality of imaging since inflamed but the tissue without infection might be misidentified as one of the infections. The PET or the position emission tomography – CT is also undergoing investigation as one of the modality of imaging for the LVADI. Moreover, it has become very useful in the identification of the LVAD components infection and the response to the therapy. PET – CT may also be significant in revealing some of the unsuspected distant sites of the infection like the paravertebral abscess. Often, given the prolonged bacteremia that in most cases accompanies the DLIs, particularly with the pathogens such as the pseudomonas aeruginosa or the staphylococcus aureus, the evaluation for the metastatic infection sites can be vital.

In light of fixing such failures, the understanding of the evolution and the epidemiology of the LVAD DLI has improved the in the recent years. Moreover, there has already been an initial stride for the optimization of the LVAD techniques of implementation and the adjustment of the driveline exit site maintenance as the processes for prevention of the DLI. However, more studies are urgently needed for the definition of the evidence-based treatment of such infections that include the necessity of the device, choice of the biofilm-active antibiotic regimens, and the utility of suppressive antibiotics.

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