**2. İABP**

IABPs are the most widely used MCS devices since its introduction in the 1960s. The IABP is a balloon catheter, which is generally inserted into the aorta through the femoral artery (**Figure 1**). At the beginning of diastole, the balloon inflates and the device increases the coronary perfusion. By systole, the balloon deflates and left ventricular after-load reduces and increases the cardiac output. So the pump decreases the left ventricular stroke work, myocardial oxygen requirements, and increased cardiac output. In this manner, the balloon supports the heart indirectly. Since it is easy to insert, IABP is the most widely used form of mechanical circulatory support.

The indications for IABP usage are failure to wean from cardiopulmonary bypass, cardiogenic shock, heart failure, and acute heart attack. Although IABP is mainly used for surgical patients, the pump can be used during high-risk interventional cardiology procedures.

During acute-decompensated heart failure, IABP may help in supporting a patient who is awaiting a heart transplant in initial period, but if the patients need longer time, another p-MCS device can be replaced or long-term LVAD implantation may be required because of its limited length of use.

Before 2012, the American and European guidelines supported that implantation of IABP in cardiogenic shock recommended as a class I; but, in the IABP-SHOCK II trial study, IABP was not found to be associated with reduction in 30-day mortality in cardiogenic shock [3]. American guidelines have downgraded the recommendation for usage of the IABP from Class I to IIa, and European guidelines to Class III. Both American and European guidelines endorse the usage of other mechanical-assist devices that provide more hemodynamic support.

Absolute contraindications for IABP use are aortic insufficiency, aortic dissection-aneurysm, sepsis, and severe coagulopathy. Atherosclerosis and arterial tortuosity and left ventricular outflow tract obstruction are relative contraindications for IABP placement.

**Figure 1.** İABP.

VADs are commonly used as a temporary treatment for people waiting for a heart transplant. These devices are increasingly being used as a long-term treatment for people who have heart

**IABP Impella TandemHeart ECMO**

36 mmHg −14 mmHg

Insertion time 6–22 min 11–41 min 15–45 min 15–60 min Flow None 2.5–5.0 L/min 4.5 L/min 5.0 L/min

−7 mmHg

Leg ischemia 0.9% 3.9% 3.4–33% 18.8% Bleeding 0.8% 13% Up to 59.8% 18%

Duration of support 6 h to several weeks 6 h to several days 6 h to several days 6 h to several days

Minimal 20–30 mmHg

MAP: mean arterial pressure, PCWP: pulmonary capillary wedge pressure.

The bridge-to-transplant strategy integrating with a long-term continuous-flow VAD has played a major role in providing circulatory support during the waiting period prior to transplantation. Short-term mechanical circulatory support devices (MCS) provide good hemodynamic support for patients with cardiogenic shock and these devices are increasingly used as a bridge-todecision in patients with refractory cardiogenic shock [2]. Short-term mechanical circulatory

When cardiogenic shock is refractory to medical therapy, percutaneous mechanical circulatory support (MCS) should be considered. Subsequently, these patients might be bridged to durable MCS either as a bridge-to-candidacy/transplantation or as a destination therapy.

There are three types (**Table 1**) of well-known MCS devices including Impella (Abiomed, Danvers, MA), TandemHeart (CardiacAssist, Pittsburgh, PA), and extracorporeal membrane oxygenation (ECMO), for short-term and percutaneous application. Intra-aortic balloon pump is also uses for short-term support in cardiogenic shock with percutaneous way. These various devices can aid, restore, or maintain appropriate tissue perfusion before the develop-

Here, we discuss the patient selection, current state, ongoing advances, and implantation

IABPs are the most widely used MCS devices since its introduction in the 1960s. The IABP is a balloon catheter, which is generally inserted into the aorta through the femoral artery (**Figure 1**). At the beginning of diastole, the balloon inflates and the device increases the coronary perfusion.

failure but are not eligible for a heart transplant.

**Table 1.** The types and the characteristics of the pMCS devices.

ment of irreversible end-organ damage.

techniques of these percutaneous MCS.

**2. İABP**

MAP increase PCWP reduction

68 Heart Transplantation

support devices acutely improve hemodynamic conditions.


**Controlled release**

The use of microencapsulation technology for a controlled release application is one of the best ways to increase efficiency and minimize environmental damage. It can achieve a controlled delay of the release of the active substance until a stimulus is encountered at a specific rate, time, or situation, i.e., heating, moisture, mechanical pressure, etc. In this case, the shell acts as a protective barrier to prevent diffusion and mass loss of the active substance, and therefore maintain intact the core compounds until final use.


**Heat Transfer in Engineering**

Editors

**Moo-Yeon Lee Jae-Hyeong Seo**

MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade • Manchester • Tokyo • Cluj • Tianjin

*Editors* Moo-Yeon Lee Mechanical Engineering Dong-A University Busan Korea, South

Jae-Hyeong Seo Thermal Management R&D Center, Convergence Technology R&D Division Korea Automotive Technology Institute Cheonan-Si Korea, South

*Editorial Office* MDPI St. Alban-Anlage 66 4052 Basel, Switzerland

This is a reprint of articles from the Special Issue published online in the open access journal *Symmetry* (ISSN 2073-8994) (available at: www.mdpi.com/journal/symmetry/special issues/Heat Transfer Engineering).

For citation purposes, cite each article independently as indicated on the article page online and as indicated below:

LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. *Journal Name* **Year**, *Volume Number*, Page Range.

**ISBN 978-3-0365-3125-0 (Hbk) ISBN 978-3-0365-3124-3 (PDF)**

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**6. Antioxidant activity**

The compounds containing antioxidant activity inhibit and/or diminish the effects caused by free radicals, protecting the cells against the harmful effects of oxygenated and nitrogenous free radicals, formed during the oxidative process of the cells [49]. The evaluation of the antioxidant activity of plant material shall be determined by at least two methods, in order to obtain a slightly more complete context of this activity [50]. The use of ABTS colorimetric methods, together with DPPH, bring better reproducibility and sensitivity [51]. Given this, the antioxidant capacity of the raw extracts of the cocoa, cupuassu, pracaxi, and tucumã by-products was evaluated by the ABTS+ and DPPH methods, being performed in triplicate.

**Table 5** shows the antioxidant activities of CA, CP, PX, and TM extracts. According to the results, CP extract was the one that presented the best antioxidant activity, both by the ABTS+ and by the DPPH methods, while the CA presented the lowest values, determined by both methods. The four by-product extracts showed good results for the ABTS+ method.

These results were higher than those reported in the literature by Leong and Shui [52], who achieved values of the radical ABTS+ for some fruits, such as mango, passion fruit, pineapple, and guava that were 38.0; 5.5; 7.7; and 20.9 μM Trolox/g, respectively.

Studies have demonstrated that the ABTS<sup>+</sup> assay can be used to evaluate the antioxidant activity of a wide variety of substances [53], being commonly applied to determine the antioxidant activity in plants and based on the antioxidant capacity to neutralize the ABTS cation radical [54].

The antioxidant capacity values presented by different by-products CA, CP, PX, and TM, in addition to the vegetable sample difference, may also be related to different types of plant samples, which lead to different levels of phenolic compounds in extracts [55].

The results presented by the different by-products bring perspectives on the use of their antioxidant capabilities and may be better used in the development of new products.

#### **Table 5.**

*Values of antioxidant activity, by ABTS and DPPH methods, of raw extracts of CA [13], CP [10], PX [14], and TM [15].*