Cardiac amyloidosis-interdisciplinary approach to diagnosis and therapy.

The vast majority of cardiac amyloidosis (CA) cases are caused by light chain (AL) or transthyretin (ATTR) amyloidosis. The latter is divided into hereditary (ATTRv) and wild-type forms (ATTRwt). The incidence of ATTRwt amyloidosis has significantly increased, particularly due to the improved diagnosis of cardiac manifestations, with relevant proportions in patient populations with heart failure (HF) and preserved ejection fraction (HFpEF). Cardiac amyloidosis should be suspected in HF with indicative clinical scenarios/"red flags" with typical signs of CA in echocardiography. Further noninvasive imaging (cardiovascular magnetic resonance imaging, scintigraphy) and specific laboratory diagnostics are important for the diagnosis and typing of CA into the underlying main forms of ATTR and AL amyloidosis. The histopathologic analysis of an endomyocardial biopsy is necessary if noninvasive diagnostic methods do not enable reliable typing of CA. This is crucial for initiating specific therapy. Therapy of HF in CA is largely limited to the use of diuretics in the absence of evidence on the benefit of classic HF therapy with neurohormonal modulators. Innovative therapies have been developed for amyloidosis with improvement in organ protection, prognosis, and quality of life. These include specific cytoreductive therapies for monoclonal light-chain disease in AL amyloidosis and pharmacologic stabilization or inhibition of transthyretin expression in ATTR amyloidosis. Since the CA underlying amyloidosis is a systemic disease also affecting other organ systems, close interdisciplinary cooperation is crucial for rapid and effective diagnosis and therapy.

Dilated cardiomyopathies and non-compaction cardiomyopathy.

Dilated cardiomyopathy (DCM) is the most common form of cardiomyopathy and one of the most common causes of heart failure. It is characterized by left or biventricular dilation and a reduced systolic function. The causes are manifold and range from myocarditis to alcohol and other toxins, to rheumatological, endocrinological, and metabolic diseases. Peripartum cardiomyopathy is a special form that occurs at the end of or shortly after pregnancy. Genetic mutations can be detected in approximately 30-50% of DCM patients. Owing to the growing possibilities of genetic diagnostics, increasingly more triggering variants and hereditary mechanisms emerge. This is particularly important with regard to risk stratification for patients with variants with an increased risk of arrhythmias. Patient prognosis is determined by the occurrence of heart failure and arrhythmias. In addition to the treatment of the underlying disease or the elimination of triggering harmful toxins, therapy consists in guideline-directed heart failure treatment including drug and device therapy.

Reperfusion injury in skeletal muscle: interaction of osmotic and colloid-osmotic pressure in the initial reperfusate for oedema prevention.

Previous studies from the authors' laboratory have shown that controlled limb perfusion after prolonged, acute ischaemia minimizes reperfusion injury. The present study was performed to investigate the role of osmotic and colloid-osmotic pressure in the initial reperfusate in order to reduce postischaemic limb oedema and subsequent reperfusion injury. A total of 96 isolated rat hindlimbs were used: 18 were perfused immediately after amputation (no ischaemia; untreated) and 78 limbs were subjected to 4 h of warm ischaemia in a moist chamber. Thereafter eight limbs were used to investigate the effects of the addition of mannitol to the initial reperfusate. The remaining 70 limbs received controlled reperfusion (modified reperfusate with various osmotic (315-580 mosmol/l) and colloid-osmotic pressure (0-50 mmHg. perfusion pressure 50 mmHg) during the first 30 min after ischaemia. Controlled reperfusion was always followed by uncontrolled reperfusion (30 min. perfusion pressure 100 mmHg) to simulate the clinical condition where normal blood perfusion at systemic pressure will follow controlled reperfusion. Functional recovery, limb weight, water content of the soleus muscle, limb flow and tissue high-energy phosphates were assessed at the end of the experiment. Results show that a reperfusate without colloid-osmotic pressure (i.e. without macromolecules) produces severe limb oedema (84.6(2.0)% water content) and allows no functional recovery after prolonged warm ischaemia. Addition of mannitol to the initial reperfusate does not prevent severe reperfusion injury. In contrast, a hyperosmotic reperfusate with a colloid-osmotic pressure of 26 mmHg effectively prevents limb oedema (78.6(0.9)% water content, 110.8(2.4)% of control weight). Physiological osmotic pressure (315 mosmol/l), however, will not reduce oedema formation (82.7(0.4)% water content). Furthermore, colloid-osmotic pressure > 26 mmHg increases the viscosity of the reperfusate (flow decreases to < 50% of control) and does not allow an optimal functional recovery. Macromolecules used to create the colloid-osmotic pressure should be of similar molecular weight to albumin (69,000 Da); those with a smaller molecular weight (e.g. hydroxyethyl starch40,000/0.5) produce excessive limb oedema (184.9(13.5)% control weight; 85.7(1.4)% water content) without functional recovery (0% control contractions). The present data suggest that after prolonged limb ischaemia: (1) addition of mannitol to a crystalloid solution does not prevent oedema; (2) hyperosmotic reperfusates (380-480 mosmol/l) with a colloid-osmotic pressure of 26 mmHg are most effective in preventing limb oedema; and (3) macromolecules used to achieve colloid-osmotic pressure should have a molecular weight similar to albumin.

Studies of reperfusion injury in skeletal muscle: preserved cellular viability after extended periods of warm ischemia.

Four hours of complete normothermic ischemia in the rat hindlimb has been thought to produce extensive and irreversible damage and no possibility of salvage by reperfusion. This study tests the hypothesis that, in contrast to conventional wisdom, the cellular integrity is preserved after 4 hours of complete warm ischemia and control of the initial reperfusion can restore immediate contractility in these limbs. Ninety-two rat hindlimbs were isolated and 26 of the 92 did not undergo ischemia or reperfusion and served as controls. Sixty-six limbs were subjected to 4 hours of complete warm ischemia; of those 34 were assessed after the ischemic period without reperfusion and 32 were reperfused after the ischemic period. Nineteen hindlimbs were reperfused with Krebs-Henseleit buffer at a pressure of 100 mmHg to simulate embolectomy (uncontrolled reperfusion). In 13 legs a modified reperfusate at a pressure of 60 mmHg was used during the initial 30 minutes followed by an additional 30 minutes of reperfusion with 100 mmHg using Krebs-Henseleit buffer (controlled reperfusion). At the end of each experimental protocol, limbs were assessed by the following methods: muscle contraction, water content, volume, high energy phosphate content, muscle pH, effluent pH, mitochondrial function, ultrastructure, flow, and creatinkinase activity in the effluent. Data are expressed as mean +/- SEM. Significant differences were defined as probabilities for each test of p less than 0.05. Four hours of complete warm ischemia resulted in a severe reduction of adenosine triphosphate (4.0 +/- 0.8 vs 27.1 +/- 6.7 mumol/gm protein, p less than 0.001) and no contractions could be stimulated (0.0 +/- 0.0% CC). Muscle pH fell to 6.3 +/- 0.1 (p less than 0.001), and ultrastructural damage occurred (score 3.3 +/- 0.4 vs 0.8 +/- 0.1, p less than 0.002). However, there was only a slight increase in water content of the soleus muscle (78.7 +/- 0.2% vs 74.8 +/- 1.1%, p less than 0.05) without increase in limb volume (103.6 +/- 0.6% CV). In addition mitochondrial function was preserved well: mitochondrial oxidative phosphorylation capacity remained at 94% of control levels, ST3 at 93%, and ADP/O at 100% of control. Most importantly, controlled reperfusion restored immediate contractility in all limbs and was superior in all parameters investigated compared to uncontrolled reperfusion. These data support our inference that necrosis of skeletal muscle does not invariably occur after four hours of complete warm ischemia and suggest that muscle salvage by controlled reperfusion is possible after at least 4 hours of warm ischemia.

Avoiding reperfusion injury after limb revascularization: experimental observations and recommendations for clinical application.

This study tests the hypothesis that reperfusion injury is the principal cause of limb loss after acute arterial occlusion and that this injury is avoidable. Of 61 isolated hindlimbs amputated at the level of the hip joint, 17 were controls (group I), 5 were perfused without ischemia to establish the validity of the model (group II), and 15 underwent 4 hours of ischemia at room temperature without reperfusion (group III). Acute embolectomy was simulated in 24 limbs after 4 hours of ischemia; 12 were reperfused with standard Krebs-Henseleit solution at 100 mm Hg (group IV), and 12 were reperfused under controlled conditions (i.e., 37 degrees C, 50 mm Hg) with substrate-enriched modified reperfusate (group V). Leg volume, water content, contractile function, and high-energy phosphate content were assessed and data were expressed as mean +/- SD. Four hours of ischemia caused a profound fall in adenosine triphosphate content (4.0 vs 26.0 mmol/L/gm of protein, p less than or equal to 0.001). Uncontrolled reperfusion resulted in severe reperfusion injury; massive edema developed (83% vs 75%, p less than or equal to 0.01), leg volume increased markedly (21.5% above control, p less than or equal to 0.001), and no contractile function followed electrical stimulation. In contrast, controlled reperfusion resulted in normal water content (76.9% vs 75.0%, NS) and minimal change of leg volume (5.5% +/- 5% of control, NS), replenished adenosine triphosphate completely (24.2 vs 26.4 mmol/L/gm of protein, NS), and restored immediate contractile function in all limbs (24.3% +/- 14% of control). This study shows that 4 hours of room-temperature ischemia (18 degrees C) does not produce irreversible damage of the rat hindlimb because the reperfusion injury that follows uncontrolled reperfusion can be avoided. Immediate recovery of contractile function can be restored if the conditions of reperfusion are controlled by gentle reperfusion pressure (50 mm Hg) at 37 degrees C and if a modified substrate-enriched, hyperosmotic, alkalotic, low-Ca++ reperfusate is administered.