Clinical Relevance of Troponin T Profile Following Cardiac Surgery

Background: Peak post-operative cardiac troponin T (cTnT) independently predicts mid- and long-term outcome of cardiac surgery patients. A few studies however have reported two peaks of cTnT over the first 48–72 h following myocardial reperfusion. The aim of the current study was to better understand underlying reasons of these different cTnT profiles and their possible relevance in terms of clinical outcome.

Methods: All consecutive adult cardiac surgical procedures performed with an extra-corporeal circulation during a >6 years period were retrospectively evaluated. Patients with a myocardial infarction (MI) < 8 days were excluded. cTnT profile of patients with at least one value ≥1 ng/mL value were categorized according to the time occurrence of the peak value. Univariable and multivariable analysis were performed to identify factors influencing early vs. late increase of cTnT values, and to verify the correlation of early vs. late increase with clinical outcome.

Results: Data of 5,146 patients were retrieved from our prospectively managed registry. From 953 with at least one cTnT value ≥1 ng/mL, peak occurred ≤ 6 h (n = 22), >6 to ≤ 12 h (n = 366), >12 to ≤ 18 h (n = 176), >18 to ≤ 24 h (171), >24 h (218). Age (OR: 1.023; CI: 1.016–1.030) and isolated CABG (OR: 1.779; CI: 1.114–2.839) were independent predictors of a late increase of cTnT over a limit of 1 ng/ml (p < 0.05), whereas isolated valve procedures (OR: 0.685; CI: 0.471–0.998) and cross-clamp duration (OR: 0.993; CI: 0.990–0.997) independently predicted an early elevation (p < 0.05). Delayed elevation as opposed to early elevation correlated with a higher rate of post-operative complications including MI (19.8 vs. 7.2%), new renal insufficiency (16.3 vs. 6.7%), MACCE (32.0 vs. 15.5%), or death (7.4 vs. 4.4%).

Conclusion: Profile of cTnT elevation following cardiac surgery depends on patients' intrinsic factors, type of surgery and duration of cross-clamp time. Delayed increase is of higher clinically relevance than prompt post-operative elevation.

Development of a cardiac loading device to monitor cardiac function during ex vivo graft perfusion

Background

Ex vivo heart perfusion systems, allowing continuous perfusion of the coronary vasculature, have recently been introduced to limit ischemic time of donor hearts prior to transplantation. Hearts are, however, perfused in an unloaded manner (via the aorta) and therefore, cardiac contractile function cannot be reliably evaluated.

Objectives

We aim to develop a ventricular loading device that enables monitoring of myocardial function in an ex vivo perfusion system. In this initial study, was to develop a prototype for rat experimentation.

Methods

We designed a device consisting of a ventricular balloon and a reservoir balloon, connected through an electronic check valve, which opens and closes in coordination with changes in ventricular pressure. All balloons were produced in our laboratory and their properties, particularly pressure-volume relationships, were characterized. We developed a mock ventricle in vitro test system to evaluate the device, which was ultimately tested in ex vivo perfused rat hearts.

Results

Balloon production was consistent and balloon properties were maintained over time and with use on the device. Results from in vitro and ex vivo experiments show that the device functions appropriately; hemodynamic function can be measured and compares well to measurements made in an isolated, working (loaded) rat heart preparation.

Conclusions

Our cardiac loading device appears to reliably allow measurement of several left ventricular hemodynamic parameters and provides the opportunity to control ventricular load.

Prognostic Value of Early Postoperative Troponin T in Patients Undergoing Coronary Artery Bypass Grafting

BACKGROUND

Cardiac troponin T (cTnT) is elevated after coronary artery bypass grafting surgery. The aim of this study was to determine the association between cTnT elevations between 6 and 12 hours after coronary artery bypass grafting and in-hospital outcome.

METHODS AND RESULTS

We prospectively studied 1722 patients undergoing isolated coronary artery bypass grafting. We assessed the association between conventional cTnT (749 patients) and high-sensitivity cTnT (hs-cTnT; 973 patients) 6 to 12 hours postoperatively with in-hospital major adverse cardiac or cerebrovascular events (MACCE), a composite of all-cause death, myocardial infarction, or stroke. The prespecified secondary outcome was a safety composite of MACCE, resuscitation, intensive care unit readmission or admission ≥48 hours, inotrope or vasopressor use ≥24 hours, or new-onset renal insufficiency. Among patients with a conventional cTnT measurement, 92 experienced a MACCE (12%) and 146 experienced a safety composite event (19%). Likewise, for hs-cTnT, 114 experienced a MACCE (12%) and 153 experienced a safety composite event (16%). Compared with cTnT ≤200 ng/L, each 200-ng/L increment in cTnT was associated with a monotonous increase in the odds of MACCE and the safety composite outcome. Conventional and hs-cTnT demonstrated moderate discrimination for MACCE (areas under the fitted receiver operating characteristics curve, 0.72 and 0.77 for conventional and hs-cTnT, respectively) and the safety composite outcome (areas under the fitted receiver operating characteristics curve, 0.66 and 0.74 for conventional and hs-cTnT, respectively) and resulted in improved prognostic performance when added to the EuroSCORE. At a cutoff of 800 ng/L, conventional and hs-cTnT provided clinically relevant power to rule in MACCE and the safety composite outcome.

CONCLUSIONS

cTnT levels assessed between 6 and 12 hours after coronary artery bypass grafting identify patients at increased risk of MACCE or other complications.

Re-interventions on the thoracic and thoracoabdominal aorta in patients with Marfan syndrome

The advent of multi-gene panel genetic testing and the discovery of new syndromic and non-syndromic forms of connective tissue disorders have established thoracic aortic aneurysms as a genetically mediated disease. Surgical results in patients with Marfan syndrome (MFS) provide an important benchmark for this patient population. Prophylactic aortic root surgery prevents acute dissection and has contributed to the improved survival of MFS patients. In the majority of patients, re-interventions are driven by a history of dissection. Patients undergoing elective root repair have a low risk for re-interventions on the root itself. Experienced centers have results after valve-sparing procedures at 10 years comparable with those seen after a modified Bentall procedure. In patients where only the ascending aorta was replaced during the initial surgery, re-intervention rates are high as the root continues to dilate. The fate of the aortic arch in MFS patients presenting with dissection is strongly correlated with the extent of the initial surgery. Not replacing the entire ascending aorta and proximal aortic arch results in a high rate of re-interventions. Nevertheless, the additional burden of replacing the entire aortic arch during emergent proximal repair is not very well defined and makes comparisons with patients undergoing elective arch replacement difficult. Interestingly, replacing the entire aortic arch during initial surgery for acute dissection does not protect from re-interventions on downstream aortic segments. MFS patients suffering from type B dissection have a high risk for re-interventions ultimately leading up to replacement of the entire thoracoabdominal aorta even if the dissection was deemed uncomplicated by conventional criteria. While current guidelines do not recommend the implantation of stent grafts in MFS patients, implantation of a frozen-elephant-trunk to create a stable proximal landing zone for future endovascular or open procedures has emerged as a means to address aortic arch and descending aortic pathologies.

High pre-ischemic fatty acid levels decrease cardiac recovery in an isolated rat heart model of donation after circulatory death

RATIONALE

Donation after circulatory death (DCD) could improve cardiac graft availability. However, strategies to optimize cardiac graft recovery remain to be established in DCD; these hearts would be expected to be exposed to high levels of circulatory fat immediately prior to the inevitable period of ischemia prior to procurement.

OBJECTIVE

We investigated whether acute exposure to high fat prior to warm, global ischemia affects subsequent hemodynamic and metabolic recovery in an isolated rat heart model of DCD.

METHODS AND RESULTS

Hearts of male Wistar rats underwent 20min baseline perfusion with glucose (11mM) and either high fat (1.2mM palmitate; HF) or no fat (NF), 27min global ischemia (37°C), and 60min reperfusion with glucose only (n=7-8 per group). Hemodynamic recovery was 50% lower in HF vs. NF hearts (34±30% vs. 78±8% (60min reperfusion value of peak systolic pressure*heart rate as percentage of mean baseline); p<0.01). During early reperfusion, glycolysis (0.3±0.3 vs. 0.7±0.3μmol*min^-1*g dry^-1, p<0.05), glucose oxidation (0.1±0.03 vs. 0.4±0.2μmol*min^-1*g dry^-1, p<0.01) and pyruvate dehydrogenase activity (1.8±0.6 vs. 3.6±0.5U*g protein^-1, p<0.01) were significantly reduced in HF vs. NF groups, respectively, while lactate release was significantly greater (1.8±0.9 vs. 0.6±0.2μmol*g wet^-1*min^-1; p<0.05).

CONCLUSIONS

Acute, pre-ischemic exposure to high fat significantly lowers post-ischemic cardiac recovery vs. no fat despite identical reperfusion conditions. These findings support the concept that oxidation of residual fatty acids is rapidly restored upon reperfusion and exacerbates ischemia-reperfusion (IR) injury. Strategies to optimize post-ischemic cardiac recovery should take pre-ischemic fat levels into consideration.

Controlled Reperfusion Strategies Improve Cardiac Hemodynamic Recovery after Warm Global Ischemia in an Isolated, Working Rat Heart Model of Donation after Circulatory Death (DCD)

Aims: Donation after circulatory death (DCD) could improve cardiac graft availability, which is currently insufficient to meet transplant demand. However, DCD organs undergo an inevitable period of warm ischemia and most cardioprotective approaches can only be applied at reperfusion (procurement) for ethical reasons. We investigated whether modifying physical conditions at reperfusion, using four different strategies, effectively improves hemodynamic recovery after warm ischemia.

Methods and Results: Isolated hearts of male Wistar rats were perfused in working-mode for 20 min, subjected to 27 min global ischemia (37°C), and 60 min reperfusion (n = 43). Mild hypothermia (30°C, 10 min), mechanical postconditioning (MPC; 2x 30 s reperfusion/30 s ischemia), hypoxia (no O₂, 2 min), or low pH (pH 6.8–7.4, 3 min) was applied at reperfusion and compared with controls (i.e., no strategy). After 60 min reperfusion, recovery of left ventricular work (developed pressure^*heart rate; expressed as percent of pre-ischemic value) was significantly greater for mild hypothermia (62 ± 7%), MPC (65 ± 8%) and hypoxia (61 ± 11%; p < 0.05 for all), but not for low pH (45 ± 13%), vs. controls (44 ± 7%). Increased hemodynamic recovery was associated with greater oxygen consumption (mild hypothermia, MPC) and coronary perfusion (mild hypothermia, MPC, hypoxia), and with reduced markers of necrosis (mild hypothermia, MPC, hypoxia) and mitochondrial damage (mild hypothermia, hypoxia).

Conclusions: Brief modifications in physical conditions at reperfusion, such as hypothermia, mechanical postconditioning, and hypoxia, improve post-ischemic hemodynamic function in our model of DCD. Cardioprotective reperfusion strategies applied at graft procurement could improve DCD graft recovery and limit further injury; however, optimal clinical approaches remain to be characterized.

Common Femoral Artery — Uncommon Aneurysms

Background and Aims:

Femoral artery aneurysms are rare. Their natural history, tendency to embolize or rupture are not well known.

Material and Methods:

Data of all patients seen 1996–2002 with femoral artery aneurysms at the Swiss Cardiovascular Center were analysed. Nine patients with 13 aneurysms of the common femoral artery (CFA) were identified. Only true aneurysms with a diameter of at least 2.5 cm were included. All patients were male, mean age 70 years (range: 57–85 years). Four patients had bilateral femoral aneurysms. Risk factors included hypertension (9/9), smoking (7/9). One of the aneurysms was palpable in 5/9. Four patients were asymptomatic, 5 had Fontaine class II claudication. Five patients also had an aortic aneurysm (AAA), one a thoracic aneurysm; and 6/9 popliteal aneurysms. In all patients, diagnosis was confirmed with duplex scan. Angiography was performed preoperatively.

Results:

The aneurysms were operated on electively using aneurysm secclusion and interposition grafting. There were no significant perioperative complications. Median hospital stay was 8 days.

Conclusion:

CFA aneurysms are rare. They are palpable in nearly half of the cases. They rarely cause thrombotic or embolic complications, but are almost always connected to other aneurysms. Patients with CFA aneurysms should be screened with duplex scan. Operative therapy is straightforward, few complications can be expected. Postoperative follow-up with annual duplex scans is suggested.

Rat Heterotopic Heart Transplantation Model to Investigate Unloading-Induced Myocardial Remodeling

Unloading of the failing left ventricle in order to achieve myocardial reverse remodeling and improvement of contractile function has been developed as a strategy with the increasing frequency of implantation of left ventricular assist devices in clinical practice. But, reverse remodeling remains an elusive target, with high variability and exact mechanisms still largely unclear. The small animal model of heterotopic heart transplantation (hHTX) in rodents has been widely implemented to study the effects of complete and partial unloading on cardiac failing and non-failing tissue to better understand the structural and molecular changes that underlie myocardial recovery. We herein review the current knowledge on the effects of volume unloading the left ventricle via different methods of hHTX in rats, differentiating between changes that contribute to functional recovery and adverse effects observed in unloaded myocardium. We focus on methodological aspects of heterotopic transplantation, which increase the correlation between the animal model and the setting of the failing unloaded human heart. Last, but not least, we describe the late use of sophisticated techniques to acquire data, such as small animal MRI and catheterization, as well as ways to assess unloaded hearts under "reloaded" conditions. While giving regard to certain limitations, heterotopic rat heart transplantation certainly represents the crucial model to mimic unloading-induced changes in the heart and as such the intricacies and challenges deserve highest consideration. Careful translational research will further improve our knowledge of the reverse remodeling process and how to potentiate its effect in order to achieve recovery of contractile function in more patients.

Spontaneous Dissection of Common Iliac Artery

Spontaneous dissection of the iliac artery is very rare but known as a complication of highenergy traumatic injuries and has been reported in connection with pregnancy, collagen diseases, and alpha-1-antitrypsin deficiency. The authors report a 42-year-old man with an acute dissection of the common iliac artery during exercise. Groin pain and claudication were the early symptoms. Computerized angiotomography was diagnostic. Operative iliac artery reconstruction was performed. A prerelease control computed tomography examination showed a dissection of the distal aorta and left iliac artery. To their knowledge, the combination of the 2 dissections has not been previously published.

Management of floating thrombus in the aortic arch

OBJECTIVE

Floating aortic thrombus is an underrecognized source of systemic emboli and carries a life-threatening risk of stroke when located in the aortic arch. Optimal treatment is not established in available guidelines. We report our experience in managing floating thrombi in the aortic arch.

METHODS

Consecutive patients diagnosed with a floating aortic arch thrombus at a tertiary referral center between January 2008 and December 2014 were reviewed. Perioperative and midterm outcomes were assessed.

RESULTS

Ten patients (8 female) with a median age of 56 years (range, 47-82 years) were identified. Eight patients presented with a symptomatic embolic event, and 2 patients were asymptomatic. One patient presenting with stroke due to embolic occlusion of all supra-aortic vessels died 2 days after admission. Three patients (2 asymptomatic and 1 unfit for surgery) were treated conservatively by anticoagulation, leading to thrombus resolution in 2 patients. In the third patient, the thrombus persisted despite anticoagulation, resulting in recurrent embolic events. The remaining 6 patients underwent open thrombectomy of the aortic arch during deep hypothermic circulatory arrest. All patients treated by surgery had an uneventful postoperative course with no recurrent thrombus or embolic event during follow-up. Median follow-up of all patients was 17 months (range, 11-89 months).

CONCLUSIONS

Floating aortic arch thrombus is a dangerous source of systemic emboli. Surgical removal of the thrombus is easy to perform and followed by good clinical results. Conservative treatment with anticoagulation may be considered in asymptomatic, inoperable or high-risk patients.

Completeness of Follow-Up Determines Validity of Study Findings: Results of a Prospective Repeated Measures Cohort Study

Background

Current reporting guidelines do not call for standardised declaration of follow-up completeness, although study validity depends on the representativeness of measured outcomes. The Follow-Up Index (FUI) describes follow-up completeness at a given study end date as ratio between the investigated and the potential follow-up period. The association between FUI and the accuracy of survival-estimates was investigated.

Methods

FUI and Kaplan-Meier estimates were calculated twice for 1207 consecutive patients undergoing aortic repair during an 11-year period: in a scenario A the population’s clinical routine follow-up data (available from a prospective registry) was analysed conventionally. For the control scenario B, an independent survey was completed at the predefined study end. To determine the relation between FUI and the accuracy of study findings, discrepancies between scenarios regarding FUI, follow-up duration and cumulative survival-estimates were evaluated using multivariate analyses.

Results

Scenario A noted 89 deaths (7.4%) during a mean considered follow-up of 30±28months. Scenario B, although analysing the same study period, detected 304 deaths (25.2%, P<0.001) as it scrutinized the complete follow-up period (49±32months). FUI (0.57±0.35 versus 1.00±0, P<0.001) and cumulative survival estimates (78.7% versus 50.7%, P<0.001) differed significantly between scenarios, suggesting that incomplete follow-up information led to underestimation of mortality. Degree of follow-up completeness (i.e. FUI-quartiles and FUI-intervals) correlated directly with accuracy of study findings: underestimation of long-term mortality increased almost linearly by 30% with every 0.1 drop in FUI (adjusted HR 1.30; 95%-CI 1.24;1.36, P<0.001).

Conclusion

Follow-up completeness is a pre-requisite for reliable outcome assessment and should be declared systematically. FUI represents a simple measure suited as reporting standard. Evidence lacking such information must be challenged as potentially flawed by selection bias.

The Impact of Pre-Operative Malperfusion on Outcome in Acute Type A Aortic Dissection: Results From the GERAADA Registry

BACKGROUND

Malperfusion adversely affects outcomes in patients with acute type A aortic dissection, but reliable quantitative data are lacking.

OBJECTIVES

The aim of this study was to analyze the impact of various forms of malperfusion on early outcome.

METHODS

A total of 2,137 consecutive patients enrolled in GERAADA (German Registry for Acute Aortic Dissection Type A) who underwent surgery between 2006 and 2010, of whom 717 (33.6%) had any kind of pre-operative malperfusion, were retrospectively analyzed.

RESULTS

All-cause 30-day mortality was 16.9% and varied substantially according to the number of organ systems affected by malperfusion (none, 12.6%; 1 system, 21.3%; 2 systems, 30.9%; 3 systems, 43.4%; p < 0.001). Pre-operative cerebral malperfusion, comatose state, peripheral malperfusion, visceral malperfusion, involvement of supra-aortic branches, coronary malperfusion, and renal malperfusion were all independent predictors of developing any post-operative malperfusion syndrome. When survival was considered, age, peripheral malperfusion, involvement of supra-aortic branches, coronary malperfusion, spinal malperfusion, a primary entry in the descending aorta, and pre-operative comatose state were independent predictors, again with increasing significance.

CONCLUSIONS

Malperfusion remains a severe clinical condition with strong potential for adverse outcomes in patients undergoing surgery for acute type A aortic dissection. The GERAADA registry suggests that the impact of the number of organs involved and the type of malperfusion on outcome differs substantially. Introducing an appropriate classification system, such as "complicated" and uncomplicated" acute type A aortic dissection, might help predict individual risk as well as select a surgical strategy that may quickly resolve malperfusion.

[Ventricular assist device – Possibilities of long-term mechanical circulatory support]

In Switzerland 200’000 people suffer from congestive heart failure. Approximately 10’000 patients find themselves in an advanced state of the disease. When conservative treatment options are no longer available heart transplantation is the therapy of choice. Should this not be an option due to long waiting lists or medical issues assist device therapy becomes an option. Assist device therapy is separated in short-term and long-term support. Long-term support is nowadays performed with ventricular assist devices (VADs). The native heart is still in place and supported in parallel to the remaining function of the heart. The majority of patients are treated with a left ventricular assist device (LVAD). The right ventrical alone (RVAD) as well as bi-ventricular support (BiVAD) is rarely needed. The modern VADs are implantable and create a non-pulsative bloodflow. A percutaneous driveline enables energy supply and pump-control. Indication strategies for VAD implantations include bridge to transplant (short term support), bridge to candidacy and bridge to transplant. VADs become more and more a definite therapeutic option (destination therapy). VAD therapy might be a realistic alternative to organ transplantation in the near future.