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kounis syndrome

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 62

76. Is it true that allergic reactions can cause heart attacks?

  • Yes.
  • Kounis Syndrome is an acute coronary syndrome caused by activated mast cells releasing chemicals. It is sometimes referred to as “allergic heart attack.” In acute coronary syndrome, there is not enough blood being pumped into the heart. It is named for two of the large blood vessels supplying oxygen to the heart, the coronary arteries. When not enough blood is getting to the heart via the coronary arteries, it can damage heart muscle, sometimes permanently. Heart attack and angina are examples of acute coronary syndromes.
  • In Kounis Syndrome, mast cells become activated, releasing lots of chemicals. These chemicals can irritate the coronary artery, causing it to spasm. This spasm reduces the amount of blood getting to the heart. Sometimes, mast cell activation can trigger the formation of a clot. A clot can be the reason not enough blood is passing through the artery.
  • Several of the molecules released by mast cells can affect the cardiovascular system and contribute to causing Kounis Syndrome. Histamine and leukotrienes can cause the coronary artery to narrow. It can also activate platelets, helping a clot to form. Both tryptase and chymase can cause clots formed elsewhere to break off and get stuck in the coronary artery.
  • Mast cells also help regulate an important molecule called angiotensin II. Angiotensin II is a powerful regulator of blood pressure and can cause the coronary artery to narrow and tighten up.
  • People with Kounis Syndrome may have a history of coronary artery disease. Some patients have a stent in the coronary artery from a previous coronary issue. A stent is a tube that helps keep the blood vessel the right size so that the heart gets the blood it needs. However, many patients with Kounis Syndrome do not have any history of problems with their heart or blood vessels.
  • The symptoms of Kounis Syndrome sometimes look just like the symptoms of any other mast cell reaction or anaphylaxis, making it hard to know that a person is having Kounis Syndrome. Chest pain, irregular heart beat, the heart beating too fast or too slow, and palpitations are all common symptoms of Kounis Syndrome.
  • Another tricky thing about Kounis Syndrome is that it doesn’t always show up on the tests we use to look for heart attack or coronary issues. Because of this, doctors don’t always realize what is happening. Some people do have positive results to these tests, things like EKG, echocardiogram, chest x-ray, and bloodwork to look at levels at cardiac enzymes or troponin. Cardiac enzymes and troponins are often high in a person who is having a heart attack but are sometimes normal for patients with Kounis Syndrome.
  • In order to manage Kounis Syndrome, patients may need treatment for both the allergic reaction and the coronary syndrome.
  • Treatment for the allergic reaction is similar to anaphylaxis treatment: an H1 antihistamine like Benadryl, an H2 antihistamine like famotidine, a corticosteroid like methylprednisolone, IV fluids, and sometimes epinephrine, if that’s appropriate. Please note that epinephrine is not always appropriate for patients who have Kounis Syndrome because epinephrine can actually also cause the coronary artery to narrow.
  • Treatment for the cardiovascular aspect of Kounis Syndrome is very dependent upon symptoms and test results. Calcium channel blockers like verapamil, aspirin, and nitroglycerin are commonly used. Importantly, some of the common medications used to manage coronary syndrome are not safe for mast cell patients. These medications include beta blockers like metoprolol or atenolol, and, to a lesser extent, ACE inhibitors like lisinophil. These medications can interfere with epinephrine so epinephrine may not work if a patient needs it for anaphylaxis.
  • Anything that triggers mast cell activation can cause Kounis Syndrome, including emotional stress.

For additional information, please visit the following posts:
Kounis Syndrome: Subtypes and effects of mast cell mediators (Part 1 of 4)
Kounis Syndrome: Diagnosis (Part 2 of 4)
Kounis Syndrome: Treatment (Part 3 of 4)
Kounis Syndrome: Stress (Part 4 of 4)
Beta blockers and epinephrine
Cardiovascular manifestations of mast cell disease: Part 1 of 5
Cardiovascular manifestations of mast cell disease: Part 2 of 5
Cardiovascular manifestations of mast cell disease: Part 3 of 5
Cardiovascular manifestations of mast cell disease: Part 4 of 5
Cardiovascular manifestations of mast cell disease: Part 5 of 5
The Provider Primers Series: Medications that impact mast cell degranulation and anaphylaxis

Kounis Syndrome: Stress (Part 4 of 4)

The phenomenon we now called Kounis Syndrome has previously been called by names like morphologic cardiac reactions, acute carditis and lesions with basic characteristics of rheumatic carditis. It is sometimes still referred to as allergic angina or allergic myocardial infarction/heart attack depending upon the presentation. Allergic angina, which affected patients as microvascular angina, was first noted to progress to allergic heart attack in 1991.

In a small study done at a hospital, 31 patients with anaphylaxis or non-anaphylactic severe allergic reactions had higher serum troponin I than healthy control patients.  Among those 31 patients, those that experienced anaphylaxis had the highest troponin I overall.  This report, and similar findings, indicates that cardiovascular damage may be a frequent component of anaphylaxis, well beyond what is reported.

Mast cell patients often struggle to identify which is the chicken and which is the egg in the many instances of comorbid conditions. There is no such confusion here – mast cell activation causes Kounis Syndrome.  Tryptase increases in peripheral blood during a spontaneous heart attack.  However, when coronary spasm is induced with medications, there is no such increase in tryptase.  In instances where Kounis Syndrome was caused by disruption of an atherosclerotic plaque, mast cells entered the lesion and released mediators prior to the initiation of the coronary event.

Stress is well known to induce mast cell degranulation.  It has been documented in dozens of papers from various disciplines in the last twenty years. Corticotropin releasing hormone (CRH) is a stress hormone that can bind to the CRHR-1 receptor on mast cells, inducing the manufacture of VEGF. At the same time as CRH is released, neurotensin can also be released.  Experimental work has shown that stress induced mast cell degranulation can be compromised if the neurotensin receptor is blocked.

Reactive oxygen species can activate mast cells and induce sensory nerves to release substance P.  Substance P is a potent mast cell degranulator, inducing secretion of histamine and release of VEGF and other inflammatory mediators. These multiple activation pathways triggered by stress result in mast cell mediator release, which can induce coronary hypersensitivity syndromes such as Kounis Syndrome.

References:

Kounis NG, et al. Kounis Syndrome (allergic angina and allergic myocardial infarction). In: Angina Pectoris: Etiology, Pathogenesis and Treatment 2008.

Lippi G, et al. Cardiac troponin I is increased in patients admitted to the emergency department with severe allergic reactions. A case-control study. International Journal of Cardiology 2015, 194: 68-69.

Kounis NG, et al. The heart and coronary arteries as primary target in severe allergic reactions: Cardiac troponins and the Kounis hypersensitivity-associated acute coronary syndrome. International Journal of Cardiology 2015, 198: 83-84.

Fassio F, et al. Kounis syndrome: a concise review with focus on management. European Journal of Internal Medicine 2016; 30:7-10.

Kounis Syndrome: Aspects on pathophysiology and management. European Journal of Internal Medicine 2016.

Kounis NG. Kounis syndrome: an update on epidemiology, pathogenesis, diagnosis and therapeutic management. Clin Chem Lab Med 2016

Kounis NG. Coronary hypersensitivity disorder: the Kounis Syndrome. Clinical Therapeutics 2013, 35 (5): 563-571.

Alevizos M, et al. Stress triggers coronary mast cells leading to cardiac events. Ann Allergy Asthma Immunol 2014; 112 (4): 309-315.

Kounis Syndrome: Treatment (Part 3 of 4)

Kounis Syndrome treatment requires amelioration of both allergic and cardiovascular symptoms.

  • Type I KS patients may only need treatment for allergic aspects without ever progressing to heart attack.
  • Type II and III KS patients are recommended to follow acute coronary event protocol recommended by ACS.
Treatment of allergic aspects of Kounis Syndrome
Drug class Medication Dosage Notes
H1 inverse agonist Diphenhydramine 1-2 mg/kg

50mg IV is a frequent dosage used for mast cell patients experiencing anaphylaxis symptoms

 Can cause hypotension and decrease blood flow through coronary artery if given bolus; should be given slowly
H2 antagonist Ranitidine 1 mg/kg
Famotidine 40mg IV is a frequent dosage used for mast cell patients experiencing anaphylaxis symptoms
Corticosteroid Methylprednisolone or other Methylprednisolone 120 mg IV is a frequent dosage used for mast cell patients experiencing anaphylaxis symptoms Corticosteroids are not used for immediate effect, but to prevent biphasic reactions.Corticosteroid treatment in active heart attack patients has not been found to be harmful.Corticosteroids were recommended as early as 2008 by Kounis for several reasons: inhibition of eicosanoid synthesis, decreasing amount of prostaglandins, leukotrienes and thromboxanes that can be made; reduction of inflammation by increasing death receptor CD95 on some cells; synthesis of annexins, proteins that modulate inflammatory cells and their actions

 

 
Fluid support IV fluids Crystalloid normal saline; avoid colloid solution Use with caution to avoid pulmonary edema
Epinephrine Epinephrine IM dose: 0.2-0.5mg every 5-15 minutes Can contribute to myocardial ischemiaCan prolong the QTc interval

Can cause coronary vasospasm and arrhythmias, especially if given IV

Glucagon is an alternative in patients for whom epinephrine is inappropriate

 

 

Treatment of coronary syndrome in Kounis Syndrome
Drug class Medication Dosage Notes
Nitroglycerin Nitroglycerin Sublingual: 0.3-0.4 mg every five minutesIV: 5-10mcg/min, increased by 10 mcg/min every 5 minutes Causes dilation of coronary vesselsIncreases bloodflow to counteract myocardial ischemia
Calcium channel blocker Diltiazem, verapamil Example  ER dosing for verapamil: 80mg orally every eight hours, immediate release Vasodilators
NSAID Aspirin 160-325 mg Prevent clot formation
P2Y12 receptor inhibitor Clopidogrel 75mg daily Taken with aspirin to prevent clot formation; some medical bodies recommend P2Y12 inhibitors with aspirin, while others recommend aspirin alone
Glycosaminoglycan Heparin IV: 5000 IU bolus, followed by infusion of heparin until PTT 1.5-2.5 above normal Type III patientsHeparin may cause allergic reaction, especially in bolus
Opioid Fentanyl 1-2 mcg/kg Drug of choice for pain management, causes small amount of mast cell degranulation, other opiates risk large scale degranulationDoes not affect cardiac output
N/A Stent placement if vessel narrowed by atherosclerosis N/A

 

Notes:

Beta blockers are contraindicated in Kounis Syndrome for the same reason they are contraindicated in mast cell patients – they block the action of epinephrine, which complicates treatment of anaphylaxis.

IV acetaminophen is generally well tolerated by mast cell patients but is not appropriate for Kounis Syndrome. Acetaminophen reduces cardiac output and systemic vascular resistance which can cause severe low blood pressure and aggravate cardiogenic shock.

References:

Kounis NG, et al. Kounis Syndrome (allergic angina and allergic myocardial infarction). In: Angina Pectoris: Etiology, Pathogenesis and Treatment 2008.

Lippi G, et al. Cardiac troponin I is increased in patients admitted to the emergency department with severe allergic reactions. A case-control study. International Journal of Cardiology 2015, 194: 68-69.

Kounis NG, et al. The heart and coronary arteries as primary target in severe allergic reactions: Cardiac troponins and the Kounis hypersensitivity-associated acute coronary syndrome. International Journal of Cardiology 2015, 198: 83-84.

Fassio F, et al. Kounis syndrome: a concise review with focus on management. European Journal of Internal Medicine 2016; 30:7-10.

Kounis Syndrome: Aspects on pathophysiology and management. European Journal of Internal Medicine 2016.

Kounis NG. Kounis syndrome: an update on epidemiology, pathogenesis, diagnosis and therapeutic management. Clin Chem Lab Med 2016

Kounis NG. Coronary hypersensitivity disorder: the Kounis Syndrome. Clinical Therapeutics 2013, 35 (5): 563-571.

Kounis Syndrome: Diagnosis (Part 2 of 4)

Separating the symptoms of the coronary syndrome from those caused by the coincident allergic reaction is difficult.  Acute chest pain is the hallmark symptom of Kounis Syndrome. While other symptoms may be present, such as nausea, fainting, and shortness of breath, they can also be attributed to the allergic reaction.  Likewise, many of the clinical markers for KS may also appear during anaphylaxis, including cold extremities, very fast or very low heart rate, low blood pressure, palpitations, and sweating. Given the significant overlap in presentation with allergic symptoms, KS is not often diagnosed, though it likely affects a larger population than represented in literature.

Troponins and cardiac enzymes like creatinine kinase are important markers for coronary syndrome, but they are not always elevated in KS. Measurement of mast cell mediators like histamine or tryptase is not always accurate due to the short lifetime of these molecules in the body.  Released histamine is only present in blood for about eight minutes, while tryptase has a half-life of about ninety minutes.

An electrocardiogram (EKG) should be performed as part of the diagnostic process.  A number of signs have been seen in KS patients, including atrial or ventricular fibrillation, bigeminal rhythm, heart block, nodal rhythm, sinus bradycardia or tachycardia, ST segment depression or elevation, T-wave flattening or inversion, QRS or QT prolongation, and ventricular ectopics.  Beyond EKG, there are additional markers that may be present with Kounis Syndrome.  A chest x-ray may show an enlarged heart.  Echocardiogram may show dilated cardiac chambers. Angiography of the coronary artery can reveal spasm or thrombosis. In coronary biopsies, infiltration by mast cells and eosinophils may be found.  Elevation of eosinophils in the blood may also be present.

Having no history of coronary artery disease can make diagnosis more complicated for KS Type I patients, who also may have normal troponins and EKG. Dynamic cardiac MRI with gadolinium can show a subendocardial lesion in patients with KS Type I. Newer imaging techniques such as SPECT have been able to identify myocardial ischemia in KS Type I where coronary angiography had showed no irregularities.

References:

Kounis NG, et al. Kounis Syndrome (allergic angina and allergic myocardial infarction). In: Angina Pectoris: Etiology, Pathogenesis and Treatment 2008.

Lippi G, et al. Cardiac troponin I is increased in patients admitted to the emergency department with severe allergic reactions. A case-control study. International Journal of Cardiology 2015, 194: 68-69.

Kounis NG, et al. The heart and coronary arteries as primary target in severe allergic reactions: Cardiac troponins and the Kounis hypersensitivity-associated acute coronary syndrome. International Journal of Cardiology 2015, 198: 83-84.

Fassio F, et al. Kounis syndrome: a concise review with focus on management. European Journal of Internal Medicine 2016; 30:7-10.

Kounis Syndrome: Aspects on pathophysiology and management. European Journal of Internal Medicine 2016.

Kounis NG. Kounis syndrome: an update on epidemiology, pathogenesis, diagnosis and therapeutic management. Clin Chem Lab Med 2016

Kounis NG. Coronary hypersensitivity disorder: the Kounis Syndrome. Clinical Therapeutics 2013, 35 (5): 563-571.

Kounis Syndrome: Subtypes and effects of mast cell mediators (Part 1 of 4)

Kounis Syndrome (KS) is an acute coronary syndrome that arises as a direct result of mast cell degranulation during an allergic or anaphylactic reaction.

KS usually presents as chest pain during an acute allergic or anaphylactic reaction. There are three recognized variants:

Type I: Patient has no predisposing coronary artery disease.

There are two possible outcomes:

  • Coronary artery spasm with no appreciable increase in cardiac enzymes or troponins
  • Coronary artery spasm that evolves to acute myocardiac infarction (heart attack) with accompanying increase in cardiac enzymes or troponins

Type II: Patient has history of coronary artery disease. There are two possible outcomes:

  • Coronary artery spasm with no appreciable increase in cardiac enzymes or troponins
  • Plaque erosion or rupture that evolves to acute myocardiac infarction (heart attack) with accompanying increase in cardiac enzymes or troponins

Type III: Patient has history of coronary artery disease and a drug eluting coronary stent. There are two possible outcomes:

  • Coronary artery spasm with no appreciable increase in cardiac enzymes or troponins
  • Thrombosis that evolves to acute myocardiac infarction (heart attack) with accompanying increase in cardiac enzymes or troponins

A number of mast cell mediators have effects that can cause coronary spasm or thrombosis.  Beyond their direct effects, they also perpetuate an inflammatory cycle that results in activation and infiltration by inflammatory cells

Mediator Effect
Histamine Coronary vasoconstriction, activation of platelets, increase expression of tissue factor
Chymase Activation of interstitial collagenase, gelatinase, stromelysin resulting in plaque rupture, generation of angiotensin II, a powerful vasoconstrictor
Cathepsin D Generation of angiotensin II, a powerful vasoconstrictor
Leukotrienes (LTC4, LTD4, LTE4) Powerful vasoconstrictor, levels increased during acute unstable angina
Tryptase Activation of interstitial collagenase, gelatinase, stromelysin resulting in plaque rupture
Thromboxane Platelet aggregation, vasoconstriction
PAF Vasoconstriction, aggregation of platelets
Platelets Vasoconstriction, thrombosis

 

References:

Kounis Syndrome (allergic angina and allergic myocardial infarction). Kounis NG, et al. In: Angina Pectoris: Etiology, Pathogenesis and Treatment 2008.

Lippi G, et al. Cardiac troponin I is increased in patients admitted to the emergency department with severe allergic reactions. A case-control study. International Journal of Cardiology 2015, 194: 68-69.

Kounis NG, et al. The heart and coronary arteries as primary target in severe allergic reactions: Cardiac troponins and the Kounis hypersensitivity-associated acute coronary syndrome. International Journal of Cardiology 2015, 198: 83-84.

Fassio F, et al. Kounis syndrome: a concise review with focus on management. European Journal of Internal Medicine 2016; 30:7-10.

Kounis Syndrome: Aspects on pathophysiology and management. European Journal of Internal Medicine 2016.

Cardiovascular manifestations of mast cell disease (Part 1 of 5)

Mast cells are present in the cardiovascular system under normal conditions both in the heart and near vasculature, often in spaces close to nerve endings.  They perform a variety of necessary functions including participating in the pathway to generate the hormone angiotensin II, which encourages an increase in blood pressure.  Mast cells in the heart and vasculature are usually positive for both chymase and tryptase in granules. Mast cells in the cardiovascular system have also been tied to a number of conditions, including atherosclerosis, arrhythmias and aneurysm.

Mast cell patients may experience a number of cardiovascular symptoms or events. 29% of SM patients and at least 20% of MCAS patients report palpitations and supraventricular tachycardia.  31% of patients with mast cell activation disease (MCAS, MMAS, SM) experience episodic or chronic elevation in arterial blood pressure due to mast cell activation. Ventricular fibrillation, cardiac arrest and Kounis Syndrome can occur in mast cell patients due to mast cell activation.  Few cases of heart failure in SM patients have been reported.

Kounis Syndrome is an acute coronary syndrome provoked by mast cell mediator release. In one series, ten mast cell patients (5 MCAS, 3 MMAS, 2 ISM) suffered acute coronary syndromes.  These patients reported “oppressive” chest pain of the type commonly seen in ischemic cardiac events.  The triggers for these events were diverse: venom immunotherapy, mepivacaine, exercise, penicillin, general anesthesia, wasp sting, metamizole and moxifloxacin.  In seven patients, the echocardiogram was normal.  In the remaining, left ventricular hypertrophy, anteroseptal hypokinesia, medioapical hypokinesia, inferoseptal akinesis, lateral apical akinesia and left ventricular ejection fraction of 40% were found on echo. Only six patients had elevation of troponin, a test commonly used to diagnose heart attack and acute coronary syndromes.

Mast cell mediators exhibit a wide range of effects on the cardiovascular and nervous systems. Mast cell mediators can affect release of norepinephrine by sympathetic nervous system, contributing to arrhythmias.  In some instances, release of norepinephrine has been linked to sudden cardiac death, although not linked specifically to mast cell patients. Histamine actually decreases norepinephrine release by binding to H3 receptors on nerve endings.

As mentioned above, mast cells participate in modulating the level of angiotensin II. Mast cells release renin, which leads to the formation of angiotensin II. Angiotensin II then binds to AT1 receptors on sympathetic nerve endings, raising blood pressure. Angiotensin II can also cause arrhythmias without involving the nervous system.

References:

Kolck UW, et al. Cardiovascular symptoms in patients with systemic mast cell activation disease. Translation Research 2016; x:1-10.

Gonzalez-de-Olano D, et al. Mast cell-related disorders presenting with Kounis Syndrome. International Journal of Cardiology 2012: 161(1): 56-58.

Kennedy S, et al. Mast cells and vascular diseases. Pharmacology & Therapeurics 2013; 138: 53-65.

Mast cells in vascular disease: Part 1

Atherosclerosis is a very specific type of artery hardening that occurs due to accumulation of white blood cells and their inflammation of the vessel. Atherosclerosis can cause heart attacks, formation of blood clots and obstruction of major vessels. There are a number of risk factors, including tobacco smoking, high LDL cholesterol, diabetes, vitamin B6 deficiency, high C reactive protein, and many others.

Atherosclerosis is now known to be an immunoinflammatory condition, one which results from inflammation mediated by immune cells. In recent years, mast cells have been found to play an important role in the formation of atherosclerotic lesions, progression and destabilization of the lesion, which in turn causes the more significant clinical effects. In 2004, 66% of men and 47% of women in the US had heart attack or sudden cardiac death as their first symptom of atherosclerotic heart disease.

Endothelial cells line the blood vessels and form the endothelium. In atherosclerotic plaques, monocytes from the blood burrow into the endothelium. They turn into macrophages, a different kind of cell. These macrophages eat certain kinds of cholesterol and start a cycle in inflammation in the vessel wall. Platelets then stick to the inflamed places.

Mast cells are known to have a number of behaviors that affect plaque pathology. Mast cells near plaques release tryptase, which activates endothelial cells through the PAR-2 receptor. This causes a series of events that produces platelet activating factor (PAF). PAF increases the permeability and contraction of the nearby smooth muscle, which can lead to vascular events.

Increased densities of mast cells have been found in the tissue layer overlaying plaques that ruptured. It has been hypothesized that mast cell released histamine could cause coronary spasm, making the plaque more likely to rupture. In a study that looked at 44 autopsy samples of aorta with atherosclerotic lesions, there was a direct correlation found between levels of tryptase and chymase, the amount of collagen in the plaque, and the size of the endothelium involved.

Mast cells that store basic fibroblast growth factor (bFGF) are found in small vessels inside plaques. Histamine may cause leakage from those tiny vessels, which can further make the plaque more likely to rupture.   In histamine deficient mice, the plaque area was reduced in size, and expression of genes for NF-kB, matrix metalloproteinases (MMPs), and inflammatory cytokines involved in plaque progression. Histamine is also involved in acute coronary vasospasm that may result in heart attack; this is called Kounis Syndrome.

 

References:

Simon Kennedy, Junxi Wu, Roger M. Wadsworth, Catherine E. Lawrence, Pasquale Maffia. Mast cells and vascular diseases. Pharmacology & Therapeutics 138 (2013) 53–65.

Ramalho, L. S., Oliveira, L. F., Cavellani, C. L., Ferraz, M. L., de Oliveira, F. A., Miranda Corrêa, R. R., et al. (2012). Role of mast cell chymase and tryptase in the progression of atherosclerosis: study in 44 autopsied cases. Ann Diagn Pathol 17, 28–31.

Lappalainen,H., Laine, P., Pentikäinen,M. O., Sajantila,A.,& Kovanen, P. T. (2004).Mast cells in neovascularized human coronary plaques store and secrete basic fibroblast growth factor, a potent angiogenic mediator. Arterioscler Thromb Vasc Biol 24, 1880–1885.

Kounis, N. G., Mazarakis, A., Tsigkas, G., Giannopoulos, S., & Goudevenos, J. (2011). Kounis syndrome: a new twist on an old disease. Future Cardiol 7, 805–824.

Cardiovascular symptoms of MCAS

MCAS patients often have a number of cardiovascular symptoms.  In true mast cell disease fashion, these symptoms often represent both ends of the spectrum.
Heart palpitations are the most common cardiac complaint, with true rhythmic abnormalities being fairly rare.  Tachycardia is also very common, but occasionally slow heart rate (bradycardia) is reported.  In bradycardic patients, no obvious cause for this can be identified.  Both low and high blood pressure can be seen, many times in the same patient, sometimes even following one after the other in a short period of time.  These changes in blood pressure often have no clear trigger.
True syncope (fainting) is uncommon in MCAS, but presyncope (lightheadedness, weakness, dizziness or vertigo) affects the majority of patients.  These presyncope episodes can be distinct from POTS symptoms, and may not be related to position.  Some patients experience as many as several episodes a day.  When tested for POTS with tilt table, MCAS patients may or may not be positive.  However, when treated for POTS, mast cell patients in general only see mild reduction in their presyncope episodes, with little improvement in their other symptoms.
MCAS patients often complain of chest pain, which may or may not reveal ECG abnormalities.  This type of pain is generally localized specifically to the chest and does not radiate down the arm.  Chest pain must be carefully evaluated due to the potential for two rare cardiac syndromes.  Additionally, mast cell disease can indirectly cause congestive heart failure by the long term action of histamine. 
Takotsubo syndrome, or stress-induced cardiomyopathy, is caused by sudden weakening of the myocardium that causes ballooning of the left ventricle.  It can cause acute heart failure, ventricular arrhythmias, and acute heart failure.  Angiography shows that there is no coronary artery defect to explain the left ventricular abnormalities.  If the patient survives, the left ventricle typically returns to normal after about eight weeks.  This does not occur as a result of an allergic reaction, but is sometimes seen in patients with idiopathic anaphylaxis.  In 75% of patients, serum catecholamines are elevated, a finding sometimes seen in MCAS patients.  Due to severe emotional stress frequently being the trigger for the cardiac event, Takotsubo syndrome is also known as broken heart syndrome.
Kounis syndrome is also known as allergic angina or allergic myocardial infarction.  In these patients, there are no obstructive lesions in the coronary artery.  Patients suffer severe chest pain or heart attack as an extension of an allergic reaction.  Kounis syndrome is caused by mast cell activation causing vasospasm of the coronary artery.  It is not known if the mast cells effecting this pathology are normally developed mast cells or improperly developed, such as seen in mastocytosis and MCAS.  This syndrome accounts for about 0.002% of all acute heart attacks.  (An in depth post on Kounis syndrome is on the way.)
MCAS patients often experience coronary and peripheral atherosclerosis.  Some have pain due to narrowing of the vessels.  Sclerosis and poor healing is seen in many MCAS patients.  Due to the importance of mast cells in angiogenesis, long term mast cell activation can contribute to aneurysms, hemorrhoids, varicosities, hemangiomas, arteriovenous malformations and telangiectasias. 
Edema is a common finding.  Most MCAS patients who have edema have no heart abnormalities and do not have pitting edema, indicating that the edema is likely not from heart disease.  MCAS patients often have widespread edema that can shift to different parts of the body.  There is usually no detectable low albumin.  This is thought to be due to third spacing. 

References:
Afrin, Lawrence B. Presentation, diagnosis and management of mast cell activation syndrome.  2013.  Mast cells.
Molderings GJ, Brettner S, Homann J, Afrin LB. Mast cell activation disease: a concise practical guide for diagnostic workup and therapeutic options. J. Hematol. Oncol.2011; 4:10-17.
Ribatti D, Crivellato E. Mast cells, angiogenesis, and tumour growth. Biochim. Biophys. Acta Mol. Basis Dis. 2012 Jan; 1822(1): 2-8.
Glowacki J, Mulliken JB. Mast cells in hemangioma and vascular malformations.  Pediatrics 1982; 70(1):48-51.
Ribatti D, Crivellato E. Mast cells, angiogenesis, and tumour growth. Biochim. Biophys. Acta Mol. Basis Dis. 2012 Jan; 1822(1):2-8.
Glowacki J, Mulliken JB. Mast cells in hemangioma and vascular malformations. Pediatrics 1982; 70(1):48-51.
Kolck UW, Alfter K, Homann J, von Kügelgen I, Molderings GJ. Cardiac mast cells: implications for heart failure. JACC 2007 Mar 13; 49(10):1106-1108.