Reduced Coronary Blood Flow in Cardiac Tamponade: Mystery Solved

ABSTRACT: A 67-year-old male presented with several week history of progressive shortness of breath, lower extremity edema, and distended jugular veins. Transthoracic echocardiography showed moderate pericardial effusion with thickened visceral pericardium and septal bounce but no chamber collapse. Right and left cardiac catheterization showed discordance of the right and left ventricular systolic pressures during respiration and severely reduced cardiac output. There was near equalization of diastolic pressures in all four chambers suggestive of effusive-constrictive pericarditis with cardiac tamponade physiology. Simultaneous coronary angiography showed remarkably reduced coronary Thrombolysis in Myocardial Infarction (TIMI) flow (TIMI grade 2 flow). Coronary blood flow was restored to normal after pericardial drainage on repeat coronary angiography. This is the first report of reduced coronary blood flow on coronary angiography in patients with effusive-constrictive pericarditis and cardiac tamponade. Our finding complements the work of previous investigators as we show that elevated intrapericardial pressures in cardiac tamponade can reduce coronary blood flow. This is likely related to extrinsic epicardial coronary vessel compression and reduced perfusion pressures, which can lead to myocardial ischemia and eventually cardiogenic shock.

J INVASIVE CARDIOL 2012;24(12):E328-E329

Key words: cardiac tamponade, coronary blood flow, effusive-constrictive pericarditis, myocardial ischemia

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We describe a case of effusive-constrictive pericarditis and cardiac tamponade with reduced coronary blood flow in all three coronary vessels noted during cardiac catheterization. Reduced coronary blood flow was thought to be secondary to elevated intrapericardial pressures. This was confirmed on repeat catheterization as normal coronary blood flow was completely restored after pericardial drainage. Our finding complements previous work on canines and humans that used simulated cardiac tamponade models to show progressive decline in coronary blood flow with gradual increase in intrapericardial pressures.^1,2 

Case Report. A 67-year-old male presented with 2-week history of progressive dyspnea and leg swelling. Physical exam was pertinent for mild confusion, generalized lower extremity edema, and ascitis. He was hypotensive with muffled heart sounds and distended jugular veins. Transthoracic echocardiography showed moderate pericardial effusion with thickened visceral pericardium and septal bounce but no chamber collapse. Simultaneous right and left cardiac catheterization showed elevated right atrial pressure with prominent ‘x’-descent, elevated right and left ventricular (RV and LV) end-diastolic pressures, and near equalization of diastolic pressures in all four cardiac chambers (~30 mm Hg). There were discordant changes in the RV and LV systolic pressures during respiration and a dip-and-plateau sign. Cardiac index was also severely reduced (1.0 mL/min/m2); these findings were consistent with effusive-constrictive pericarditis with underlying cardiac tamponade. Coronary angiography showed no significant occlusive coronary artery disease, but markedly reduced coronary blood flow (TIMI grade 2), in all 3 coronary vessels (Movie clips 1A and 1B). Etiology of reduced coronary flow was not clear and was attributed to elevated intrapericardial pressures (24 mm Hg). We repeated coronary angiograms 2 days after pericardiocentesis, and to our surprise, coronary blood flow had returned to normal with a TIMI grade 3 flow (Movie clips 2A and 2B).This confirmed our hypothesis that reduced coronary blood flow was due to elevated intrapericardial pressures.

Discussion. The effect of pericardial pressure on canine coronary circulation has been well studied in the early 1970s and 1980s.^1,3-6 In 1975, Jaramakani et al showed that after increasing intrapericardial pressure to 24 ± 3 mm Hg in 6 awake canines, coronary blood flow in the left circumflex artery decreased 51% during diastole with negative or retrograde flow during systole.¹ They suggested that extravascular compression of epicardial vessels may limit coronary blood flow and depress cardiac function as a result of myocardial ischemia. Others have argued that coronary arterial circulation is highly resistant to myocardial ischemia with increased myocardial oxygen extraction during tamponade.⁶ Abel believed that reduced coronary flow was secondary to reduced perfusion pressure with no change in coronary vascular resistance.⁷ Kingma showed, on the other hand, that vascular resistance is increased in the subendocardium at high pericardial pressures, while Bernath suggested that reduced coronary flow may be related to an a-adrenergic mechanism.^5,8 

Skalidis et al studied the effects of elevated intrapericardial pressures on human coronary circulation in a lung cancer patient with tamponade managed with percutaneous balloon pericardiotomy.² They infused normal saline into the pericardium, and measured coronary blood flow and vascular resistance at baseline and maximal hyperemia. They showed that as intrapericardial pressure increases, there is a continuous decline in coronary blood flow due to increase in coronary vascular resistance, but unaffected hyperemic response throughout. However, maximal hyperemic flow was blunted under increased intrapericardial pressures, implying augmented susceptibility to myocardial ischemia.2 Our finding complements the work of Skalidis, as we visually illustrate that elevated intrapericadial pressures decrease diastolic coronary blood flow with partial retrograde systolic flow (Movie clips 1A and 1B). Extrinsic compression of epicardial coronary arteries and veins can lead to reduced perfusion pressures with ongoing myocardial ischemia that can manifest as angina, dyspnea, electrocardiographic changes, or shock. The presence of constriction with involvement of visceral pericardium may partially explain reduced coronary blood flow; however, post-pericardiocentesis coronary flow was back to normal. Isolated inferior ST-segment elevation with chest pain has been reported in patients with cardiac tamponade and occult malignancy.⁹ Patients after coronary artery bypass graft surgery are susceptible to increased intrapericardial pressures. This is because saphenous vein grafts are easily compressible and can collapse with increasing intrapericardial pressures. This was probably overlooked in the past as surgeons used to close the pericardium. There are anecdotal cases of saphenous vein graft compression by extracardiac tumors, localized hematomas, and drainage tubes, where patients presented with reversible myocardial ischemia or myocardial infarction.^10-13

To conclude, reduced coronary blood flow is a hallmark of elevated intrapericardial pressures and cardiac tamponade. This is the first reported coronary angiogram showing in vivo real-time reduced coronary blood flow in effusive-constrictive pericarditis and cardiac tamponade. Our finding has important implications, as we may be able to assess coronary blood flow non-invasively using Doppler ultrasound and predict eminent tamponade in the absence of chamber collapse.

Video 1. Coronary angiograms of a 67-year-old patient with effusive-constrictive pericarditis and tamponade obtained prior to pericardiocentesis. Cineograms were captured at a rate of 15 frames per second. (A) Right anterior oblique (RAO) caudal view of the left coronary artery (LCA) showing reduced coronary blood flow (TIMI grade 2 flow). (B) Left anterior oblique view of the right coronary artery (RCA) showing reduced coronary blood flow (TIMI grade 2 flow). In both movie clips, note the marked reduction of coronary flow during diastole with retrograde flow during systole indicating markedly elevated intrapericardial pressures with superimposed constriction. 

Video 2. Coronary angiograms of the same patient with effusive constrictive pericarditis with tamponade obtained 2 days post pericardiocentesis. Cineograms were similarly captured at a rate of 15 frames per second. (A) Right anterior oblique caudal view of the LCA now shows normal coronary blood flow (TIMI grade 3 flow). (B) Anteroposterior view of the RCA also shows normal coronary blood flow (TIMI grade 3 flow).

These videos are also available in the multimedia archive: Reduced Coronary Blood Flow in Cardiac Tamponade.

 References

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