How does hyperventilation cause coronary vasospasm?

Hyperventilation may be an important cause of coronary vasospasm and chest pain. 1 The mechanism likely revolves around the competition between the effects of hydrogen and calcium ions on the smooth muscle of coronary arteries. 2

Respiratory alkalosis induced by hyperventilation causes a reduction of hydrogen ions which, under physiologic conditions, compete with calcium ion, an important trigger for arterial smooth muscle contraction. Lower hydrogen ion concentrations tips the balance in favor of calcium’s effects on transmembrane channels and myofibrillar ATP-ase of the smooth muscle and causes vasoconstriction.2

In fact, hyperventilation has been used to reproduce coronary spasm during angiography in patients with non-obstructive coronary artery disease and angina symptoms.The efficacy of hyperventilation in inducing an alkalotic state during this test is verified by obtaining an arterial blood gas after 6-minutes of hyperventilation.  A basic Tris-buffer to enhance alkalotic provocation was also used in earlier studies. 2

In addition to producing spasm and angina, hyperventilation-induced alkalosis has been associated with frank transmural myocardial infarction and ischemia-related arrhythmias such as ventricular tachycardia. 2,4,5

So in the appropriate context, hyperventilation may not be so benign!

References:

  1. Freeman LJ, Nixon PGF. Chest pain and the hyperventilation syndrome-some aetiologic considerations. Postgrad Med J 1985;61:957-61. http://pmj.bmj.com/content/postgradmedj/61/721/957.full.pdf
  2. Yasue HM, Nagao S, Omote A, et al. Coronary arterial spasm and Prinzmetal’s variant form of angina induced by hyperventilation and Tris-buffer infusion. Circulation 1978;58:56-62. https://www.ncbi.nlm.nih.gov/pubmed/25720
  3. Zaya M, Mehta PK, Merz NB, etal. Provocative testing for coronary reactivity and spasm. J Am Coll Cardiol 2014; 63:103-9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3914306/pdf/nihms549572.pdf
  4. Magarian GJ, Jones S, Calverley T. Hyperventilation testing for coronary vasospasm: induction of spontaneous ventricular tachycardia in association with transmural ischemia without obstructive coronary disease. 1990; 120:1447-49. http://journal.chestnet.org/article/S0012-3692(16)52837-2/pdf
  5. Chelmowski MK, Keelan MH. Hyperventilation and myocardial infarction. Chest 1988;93:1095-96. https://www.ncbi.nlm.nih.gov/pubmed/3359829

 

 

Contributed by Ramya Chitra Mosarla, Medical Student, Harvard Medical School

How does hyperventilation cause coronary vasospasm?

My patient with acute exacerbation of heart failure also has pneumonia. How often do heart failure and pneumonia coexist?

More often than you might think! The relationship between pneumonia and heart failure (HF) appears bidirectional with pneumonia precipitating heart failure (HF) and HF predisposing to it.

Although It’s often quoted that acute respiratory tract infection accounts for 3-16% of patients hospitalized with decompensated heart failure (HF) (based primarily on small observational studies),1 a 2016 large prospective study involving nearly 100,000 HF admission from 305 US hospitals has reported “pneumonia/respiratory process” as the most common precipitating clinical factor, present in 28.2% of cases (arrhythmia and medication noncompliance came in as 2nd and 3rd).2

Interestingly, the same study reported that pneumonia/respiratory process was most prevalent among patients with preserved (≥50%) ejection fraction (EF) compared to those with borderline ( 40%-49%) or reduced (<40%) EF (33% vs 30% vs 24%, respectively). 2

Pulmonary edema may in turn predispose to bacterial pneumonia through adverse effects of edema fluid on lung bacterial defense mechanisms and establishment of a culture medium for bacterial growth by the presence of fluid in the alveolar space.3

So don’t be surprised if you have to treat for both!

 

References

  1. Thomsen RW, Kasatpibal N, Riis A, et al. The impact of pre-existing heart failure on pneumonia prognosis: Population-based cohort study. J Gen Intern Med 2008;23:1407-13. https://www.ncbi.nlm.nih.gov/pubmed/18574639
  2. Kapoor JR, Kapoor R, Ju C, et al. Precipitating clinical factors, heart failure characterization, and outcomes in patients hospitalized with heart failure with reduced, borderline, and preserved ejection fraction. JACC 2016;4:464-72. https://www.scholars.northwestern.edu/en/publications/precipitating-clinical-factors-heart-failure-characterization-and 
  3. Harris GD, Woods DE, Fine R, et al. The effect of intraalveolar fluid on lung bacterial clearance. Lung 1980; 158;91-100 Harris GD, Woods DE, Fine R, et al. The effect of intraalveolar fluid on lung bacterial clearance. Lung 1980; 158;91-100. https://link.springer.com/article/10.1007/BF02713708
My patient with acute exacerbation of heart failure also has pneumonia. How often do heart failure and pneumonia coexist?

My patient with aortic sclerosis has a loud systolic ejection murmur. What is the exact mechanism of this murmur?

We usually blame cardiac murmurs on the “turbulence” caused by blood flowing past an irregular valve surface but, believe it or not, how the murmur is created has been a matter of controversy. 1-4

For sure, murmurs are generated by disturbance of laminar blood flow (ie, turbulence) but over the years many have argued that turbulence per se fails to produce adequate acoustic force to be audible at the chest wall.2 Although challenged by some,1  the concept of “vortex shedding” borrowed from fluid dynamics is fascinating and has been proposed as a potential explanation.

Per this theory, just as a boulder causes a stream to separate and generate vortices, valves (particularly when abnormal) also create vortices. As the vortices are shed near the valve, they leave in their place relatively calm wakes which are then rapidly filled by flowing blood, creating the sound of a murmur.  

Two important variables in this theory are velocity and viscosity. When the velocity of blood flow increases substantially as in high cardiac output states (eg, fever, pregnancy), vortex shedding and the intensity of the murmur also increase. Similar phenomenon may be expected when the blood viscosity is lowered (eg, in anemia).

 

References

  1. Sabbah HN, Stein PD. Turbulent blood flow in humans: Its primary role in the production of ejection murmurs. Circ Res 1976;38: 513-24. https://www.ncbi.nlm.nih.gov/pubmed/1269101
  2. Alpert MA, Systolic murmurs. In Walker HK, Hall WD, Hurst JW. Clinical methods: The history, physical, and laboratory examinations. 3rd ed. Butterworths, Boston, 1990. https://www.ncbi.nlm.nih.gov/books/NBK345/
  3. Bruns D. A general theory of the causes of murmurs in the cardiovascular system. Am J Med 1959;27:360-74. http://www.amjmed.com/article/0002-9343(59)90002-6/fulltext
  4. Guntheroth WG. Innocent murmurs: A suspect diagnosis in non-pregnant adults. Am J Cardiol 2009;104:735-7. https://www.ncbi.nlm.nih.gov/pubmed/19699354
My patient with aortic sclerosis has a loud systolic ejection murmur. What is the exact mechanism of this murmur?

My elderly patient developed a new left bundle branch block following transcatheter aortic valve replacement. Is this a frequent occurrence?

Yes, conduction abnormalities, particularly left bundle branch block (LBBB), frequently complicate transcatheter aortic valve replacement (TAVR).

A 2016 systematic review and meta-analysis reported new-onset LBBB following TAVR and persisting at hospital discharge in 13.3%-37% of patients1; the incidence may be higher or lower depending on the type of prosthesis used.2,3 In the same systematic review, new-onset LBBB was associated with a higher risk of permanent pacemaker placement (PPI) and cardiac death during 1-year followup.   In another study, persistence of LBBB post-TAVR without PPM placement was associated with an increased risk of syncope, complete AV node block, and PPI, but not overall mortality.4

The underlying anatomy of the conduction system may help explain post-TAVR conduction complications. The AV node is located adjacent to the membranous septum, closely associated with the subaortic region and LV outflow track, giving rise to the LBB.5 Protrusion of TAVR prostheses into the LV outflow tract, the mechanical injury occurring during the predilation or the positioning of the valve, and potential trauma to the conduction system by the catheters and guidewires used in TAVR may all contribute to these complications.3,5

References

  1. Regueiro A, Altisent OA, Del Trigo M, et al. Impact of new-onset left bundle branch block and periprocedural permanent pacemaker implanation on clinical outomces in patients undergoing transcatheter aortic valve replacement: A systematic review and meta-analysis. Circ Cardiovasc Interv 2016;9:e003635. http://circinterventions.ahajournals.org/content/9/5/e003635.long
  2. Nazif, T.M., Williams, M.R., Hahn, R.T., Kapadia, S., Babaliaros, V. et al. Clinical implications of new-onset left bundle branch block after transcatheter aortic valve replacement: analysis of the PARTNER experience. Eur. Heart J. 2014;21:1599-1607. https://www.ncbi.nlm.nih.gov/pubmed/24179072
  3. Bourantas CV, Serruys PW. Evolution of transcatheter aortic valve replacement. Circ Res 2014;114:1037-1051. http://circres.ahajournals.org/content/114/6/1037
  4. Urena, M., Mok, M., Serra, V., Dumont, E., Nombela-Franco, L. et al. Predictive factors and long-term clinical consequences of persistent left bundle branch block following transcatheter aortic valve implantation with a balloon-expandable valve. J Am Coll Cardiol. 2012;60:1743-1752. https://www.ncbi.nlm.nih.gov/pubmed/23040577
  5. Piazza, N., Jaegere, P., Schultz, C., Becker, A.E., Serruys, P.W., Anderson, R.H. Anatomy of the aortic valve complex and its implications for transcatheter implantation of the aortic valve. Circ Cardiovasc Interv. 2008;1:74-81. https://www.ncbi.nlm.nih.gov/pubmed/20031657

Contributed by Salvatore D’Amato MD, Mass General Hospital, Boston, MA

My elderly patient developed a new left bundle branch block following transcatheter aortic valve replacement. Is this a frequent occurrence?

In my patient on oral anticoagulation about to undergo coronary stenting, will triple therapy (an oral anticoagulant plus two antiplatelet agents) be necessary or can I get away with double therapy (an oral anticoagulant plus a single antiplatelet agent)?

 

Patients with atrial fibrillation (AF) who need percutaneous coronary intervention (PCI) after acute coronary syndrome or for stable angina pose a treatment challenge as oral anticoagulants (OACs) and dual antiplatelet therapy (DAPT) are often used concurrently to decrease the risk of systemic thromboembolism and stent thrombosis. However, “triple therapy”, including aspirin, a P2Y12 inhibitor, and an OAC (eg, warfarin or a direct oral anticoagulant-DOAC), also increases the risk of bleeding, necessitating several recent landmark trials to better address the subject.

Two modest-sized RCTs (WOEST and ISAR-TRIPLE) reported that when compared to triple therapy (DAPT plus warfarin), double therapy (single antiplatelet agent plus INR-targeted warfarin) is associated with reduced risk of bleeding complications without an increased risk of thrombotic events. 1,2

Two larger RCTs, PIONEER AF-PCI and RE-DUAL PCI, studied rivaroxaban and dabigatran, respectively, in patients with non-valvular AF undergoing PCI and found a reduction in bleeding events in patients receiving double therapy (single antiplatelet agent plus DOAC) compared to triple therapy (DAPT plus warfarin), without an increased risk of thrombotic complications. 3,4

Collectively, these studies suggest that it may be safe to treat patients with increased risk of bleeding with double therapy (even immediately following PCI) without an increase in thrombotic events. If triple therapy is elected, duration should be minimized, clopidogrel should be preferred over more potent P2Y12 inhibitors, and a PPI should be considered.

 

References:

  1. Dewilde WJ, Oirbans T, Verheugt FW, et al. Use of clopidogrel with or without aspirin in patients taking oral anticoagulant therapy and undergoing percutaneous coronary intervention: an open-label, randomised, controlled trial. Lancet. 2013;381:1107-15. https://www.ncbi.nlm.nih.gov/pubmed/23415013
  2. Fiedler KA, Maeng M, Mehilli J, et al. Duration of triple therapy in patients requiring oral anticoagulation after drug-eluting stent Implantation: The ISAR-TRIPLE Trial. J Am Coll Cardiol. 2015;65:1619-29. https://www.ncbi.nlm.nih.gov/pubmed/25908066
  3. Gibson CM, Mehran R, Bode C, et al. Prevention of bleeding in patients with atrial fibrillation undergoing PCI. N Engl J Med. 2016;375:2423-2434. http://www.nejm.org/doi/pdf/10.1056/NEJMoa1611594
  4. Cannon CP, Bhatt DL, Oldgren J, et al. Dual antithrombotic therapy with dabigatran after PCI in atrial fibrillation. N Engl J Med. Published online, Aug, 27, 2017. http://www.nejm.org/doi/pdf/10.1056/NEJMoa1708454

 

Contributed by Amulya Nagarur, MD, Mass General Hospital, Boston, MA

In my patient on oral anticoagulation about to undergo coronary stenting, will triple therapy (an oral anticoagulant plus two antiplatelet agents) be necessary or can I get away with double therapy (an oral anticoagulant plus a single antiplatelet agent)?

Do most patients with mycotic aneurysms have endocarditis?

No! In fact, the great majority of patients who develop mycotic aneurysm (MAs) in the postantibiotic era have no evidence of endocarditis1-3.

MAs are thought to be related to microbial arteritis due to blood stream infection of any source with implantation of circulating pathogen (usually bacterial) in atherosclerotic, diseased, or traumatized aortic intima. Plus, MAs may develop due to an adjacent infectious process (eg, vertebral osteomyelitis), either through direct extension or via lymphatic vessels, pathogen seeding of vasa vasorum, or infection of a pre-existing aneurysm1,2.  All these factors may occur in the absence of endocarditis.

Many of your patients may be at risk of MA such as those with advanced age or history of diagnostic or therapeutic arterial catheterization, illicit intravascular drug use, hemodialysis and depressed host immunity1-3..  Staphylococcus aureus, Salmonella sp, S. epidermidis and Streptococcus sp are common culprits in descending order1-3.

So think of MA in your patient with recent blood stream infection,  particularly due to S. aureus or Salmonella sp, in the setting of persistent signs of infection  with or without evidence of endocarditis.

Final Fun Fact: Did you know that the term “mycotic aneurysm” is a misnomer, having been first introduced by Sir William Osler to describe aneurysms of the aortic arch in a patient with (you guessed it) bacterial not fungal endocarditis?

References:

  1. Gomes MN, Choyke PL, Wallace RB. Infected aortic aneurysms: A changing entity. Ann Surg 1992;215:435-42. https://www.ncbi.nlm.nih.gov/pubmed/1616380
  2. Muller BT, Wegener OR, Grabitz K, et al. Mycotic aneurysms of the thoracic and abdominal aorta and iliac arteries: Experience with anatomic and extra-anatomic repair in 33 cases. J Vasc Surg 2001;33:106-13. https://www.ncbi.nlm.nih.gov/pubmed/11137930
  3. Mukherjee JT, Nautiyal A, Labib SB. Mycotic aneurysms of the ascending aorta. Tex Heart Inst J 2012;39:692-5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3461658/
Do most patients with mycotic aneurysms have endocarditis?

Does methotrexate reduce the risk of cardiovascular events in patients with rheumatoid arthritis?

The weight of the evidence suggests that methotrexate reduces the overall risk of cardiovascular events (CVEs)—including myocardial infarction, congestive heart failure, stroke, and or major adverse cardiac events—in RA patients (RR 0.72, 95% CI 0.57-0.91)1.

Aside from its effect on controlling systemic inflammation, methotrexate has also been shown to increase HDL and reduce total cholesterol/HDL ratio in patients with RA compared with treated non-RA controls2. In vitro, methotrexate appears to activate mechanisms involved in reverse transport of cholesterol out of the cell to the circulation for eventual excretion3. Not surprisingly then, methotrexate has also been reported to decrease atherosclerotic plaque burden measured by carotid artery intima-media thickness2.

We tend to think of RA as a disease that primarily causes arthritis but its effects may extend far beyond the joints. Patients with RA have an increased risk of cardiovascular deaths compared to the general population4, likely due to a variety of factors, including accelerated atherosclerosis secondary to chronic inflammation. At baseline, RA patients also have an unfavorable lipid profile with decreased HDL and higher total cholesterol/HDL ratio.

Fun Final Fact: Did you know that methotrexate is on the WHO Model List of Essential Medicines (April 2015) not only as a cancer drug but for treatment of RA as well5?

References:

  1. Roubille C, Richer V, Starnino T, McCourt C, McFarlane A, Fleming P, Siu S, Kraft J, Lynde C, Pope J, Gulliver W, Keeling S, Dutz J, Bessette L, Bissonnette R, Haraoui B. The effects of tumour necrosis factor inhibitors, methotrexate, non-steroidal anti-inflammatory drugs and corticosteroids on cardiovascular events in rheumatoid arthritis, psoriasis and psoriatic arthritis: a systematic review and meta-analysis. Ann Rheum Dis. 2015;74:480-9. https://www.ncbi.nlm.nih.gov/pubmed/25561362
  2. Georgiadis AN, Voulgari PV, Argyropoulou MI, Alamanos Y, Elisaf M, Tselepis AD, Drosos AA. Early treatment reduces the cardiovascular risk factors in newly diagnosed rheumatoid arthritis patients. Semin Arthritis Rheum 2008;38:13-9. https://www.ncbi.nlm.nih.gov/pubmed/18191989
  3. Reiss AB, Carsons SE, Anwar K, Rao S, Edelman SD, Zhang H, Fernandez P, Cronstein BN, Chan ES. Atheroprotective effects of methotrexate on reverse cholesterol transport proteins and foam cell transformation in human THP-1 monocyte/macrophages. Arthritis Rheum 2008;58:3675-83. https://www.ncbi.nlm.nih.gov/pubmed/19035488
  4. Aviña-Zubieta JA, Choi HK, Sadatsafavi M, Etminan M, Esdaile JM, Lacaille D. Risk of cardiovascular mortality in patients with rheumatoid arthritis: a meta-analysis of observational studies. Arthritis Rheum 2008; 59:1690-7. https://www.ncbi.nlm.nih.gov/pubmed/19035419
  5. WHO Model List of Essential Medicines (April 2015). http://www.who.int/medicines/publications/essentialmedicines/en/

 

Contributed by Brian Li, Medical Student, Harvard Medical School

Does methotrexate reduce the risk of cardiovascular events in patients with rheumatoid arthritis?