Subendocardial Ischemia Caused by Acute Severe Aortic Regurgitation Due to Aortic Root Dissection: A Case Report and Literature Review

Abstract

Electrocardiogram (ECG) findings showing ST-segment depression in a wide range of leads and ST-segment elevation in aVR are found in patients with acute coronary syndrome with multivessel coronary lesions and left main trunk lesions. A 64-year-old man with a history of eosinophilic granulomatosis presented with chest pain and dyspnea. Although an ECG showed the above findings, he was diagnosed with acute severe aortic regurgitation (AR) complicating aortic root dissection and successfully underwent urgent Bentall operation. These ECG findings indicated that acute severe AR caused subendocardial ischemia.

Introduction

Acute aortic regurgitation (AR) is usually caused by type A aortic dissection, infective endocarditis, or blunt trauma that leads to advanced heart failure and early death. Among the complications of acute type A aortic dissection, AR is common and is seen in 41-76% of patients (1). It is well known that flaps and acute AR are found on echocardiography and contrast-enhanced computed tomography (CT), especially in aortic root dissection. In contrast, there are few reports describing the electrocardiogram (ECG) findings when dissection has not progressed to coronary ostium. Acute AR may reduce myocardial perfusion by rapidly increasing the left ventricular (LV) end-diastolic pressure and decreasing the coronary blood flow (2).

We herein report a case of subendocardial ischemia with ECG findings due to acute severe AR complicating aortic root dissection.

Case Report

A 64-year-old man had a history of eosinophilic granulomatosis with polyangiitis and had been taking prednisolone. He presented to the emergency department with chest pain and dyspnea that had persisted for an hour. He also had a history of bronchial asthma but had never had such symptoms before. His blood pressure was 98/23 mmHg, heart rate was 84 bpm, and percutaneous oxygen saturation was 91% under 8 L oxygen inhalation. A blood gas analysis revealed an elevated lactate level of 3.8 mmol/L. As basic physical findings, marked moist rales and diastolic heart murmur were confirmed. Troponin T was 0.019 ng/mL and creatine kinase (CK)-MB was 8 U/L on admission. Chest X-ray showed pulmonary congestion (Fig. 1). An ECG revealed ST-segment depression in a wide range of leads and ST-segment elevation in aVR (Fig. 2). These findings are known to be found in patients with acute coronary syndrome (ACS) with multivessel coronary lesions and left main trunk lesions. However, transthoracic echocardiography (TTE) showed a normal LV systolic function (Supplemental Material) but also revealed severe AR with flaps in the LV outflow tract (Fig. 3A, B). The patient was thus diagnosed with acute aortic root dissection on contrast-enhanced CT (Fig. 4A, B). Furthermore, CT showed findings of circumferential subendocardial ischemia (Fig. 5).

Figure 1.

Chest X-ray findings on admission. Chest X-ray showed pulmonary congestion.

Figure 2.

ECG findings on admission. The ECG showed ST-segment depression in a wide range of leads and ST-segment elevation in aVR. Sweep speed was 25 mm/s, 10 mm/mV.

Figure 3.

Bedside echocardiography findings. (A) Flaps were found in the left ventricular (LV) outflow tract (yellow arrows). (B) Transthoracic echocardiography revealed severe aortic regurgitation.

Figure 4.

Contrast-enhanced CT findings. (A) Axial CT scan. (B) Coronal CT scan. CT revealed type A aortic dissection with flaps in the LV outflow tract.

Figure 5.

Subendocardial ischemia. CT showed findings of circumferential subendocardial ischemia (yellow arrows).

The patient underwent successful Bentall operation with a 27-mm Inspiris^Ⓡ and a 30-mm Gelweave Valsalva graft^Ⓡ. Intraoperative findings revealed that the left and right coronary ostium were intact. The CK-MB level on the day after surgery was 22 U/L. Coronary CT performed 10 days after surgery showed no significant stenotic lesions in the main trunk of the coronary arteries (Fig. 6). He was discharged 28 days later. The ECG at discharge showed only a high LV potential and a slight ST-segment depression (Fig. 7).

Figure 6.

Coronary CT performed 10 days after Bentall operation. CT showed no significant stenotic lesions in the main trunk of the coronary arteries.

Figure 7.

ECG findings at discharge 28 days later. The ECG at discharge showed only a high LV potential and a slight ST-segment depression. Sweep speed was 25 mm/s, 10 mm/mV.

Discussion

We reported a patient diagnosed with subendocardial ischemia due to acute severe AR complicating aortic root dissection. Subendocardial ischemia reportedly occurs in patients with chronic severe AR and normal coronary arteries (2). The causes are increased oxygen demand due to tachycardia and increased LV end-diastolic pressure as well as a decreased coronary blood flow and oxygen supply due to low aortic diastolic pressure. The normal coronary flow pattern is predominantly diastolic but can change to systolic predominance in the setting of severe AR (3). Furthermore, low diastolic aortic root pressure and the Venturi effect of the regurgitant jet at the coronary ostium cause retrograde diastolic coronary blood flow. George et al. reported that transesophageal echocardiography (TEE) showed a retrograde blood flow from the left main trunk to the aorta during LV diastole in a patient with acute severe AR (4). Our patient had a blood pressure of 98/23 mmHg on admission, and the diastolic blood pressure was extremely low. In addition, the patient had a high pulmonary capillary wedge pressure of 22 mmHg at the start of surgery, almost equal to the diastolic blood pressure. Intraoperative findings and postoperative coronary CT showed no organic stenosis or occlusion of the coronary arteries. Therefore, hemodynamic subendocardial ischemia due to acute severe AR may have resulted in such ECG findings. Fig. 5 suggests the occurrence of circumferential subendocardial ischemia. However, although the intraoperative findings showed that the coronary ostium was intact, it is possible that a decrease in the coronary blood flow occurred, as the dissection extended close to the coronary artery. Furthermore, Fig. 5 is unsharp because it is not ECG-gated, but myocardial ischemia of the ventricular septum appears to be biased towards the right ventricle (RV). This may mean that volume loading due to acute severe AR increases LV pressure followed by RV pressure, and the RV side, which is vulnerable to pressure loading, leads to significant myocardial ischemia. In this case, despite subendocardial ischemic condition, TTE showed a normal LV systolic function. When cardiac output decreases due to acute severe AR, compensatory sympathetic hyperactivity causes cardiac hypercontraction and tachycardia. This increases the cardiac work, but a low diastolic blood pressure leads to subendocardial ischemia without an adequate coronary blood flow. However, since it is not a transmural ischemia, the LV systolic function on TTE is maintained.

We searched the PubMed medical database on November 30, 2021, for all articles published on cases of acute AR. The following search terms were used: “acute aortic regurgitation”. Among them, the case reports of acute AR were summarized (Table) (5-30). Type A aortic dissection, infective endocarditis, trauma, fibrous strand rupture of aortic valve, and iatrogenicity have been reported as causes of acute AR. The clinical course of acute AR varies from hours to weeks, depending on the etiology, but aortic dissection and fibrous strand rupture are particularly urgent and often present with shock and acute heart failure. Relatively few studies have described the ECG findings of patients with acute AR. Only George et al. reported the ECG findings of global ischemia, similar to our case (4). Although not only TTE but also TEE is extremely important in elucidating the etiology of acute AR, it is difficult to perform TEE when hemodynamics are unstable. In addition, TEE is relatively invasive and is not recommended preoperatively, especially for aortic dissection. For urgent conditions, ECG and TTE, which can be performed in a short time and at the bedside, are very useful diagnostic modalities. In our case, severe ACS was suspected based on symptoms and ECG findings, but aortic root dissection could be quickly and accurately diagnosed by TTE and CT and successfully treated. In the ECG showing subendocardial ischemia, it is recommended to evaluate hemodynamics associated with increased LV end-diastolic pressure as well as ACS.

Table.

List of Case Reports of Acute Aortic Regurgitation.

Reference	Age, sex	Clinical scenario and etiology	Symptoms and objective findings	ECG	TEE, others	Outcome
(5)	73, M	Dilated aortic root and rupture of fibrous strand	Shock	Global ischemia	Intraoperative	AVR
(6)	51, M	IE	Fever, back pain and diastolic murmur	NA	Preoperative	AVR
(7)	30, M	IE	Fever, shortness of breath and unilateral pulmonary edema	NA	Preoperative	Bentall
(8)	17, M	Traumatic aortic root rupture	Wide pulse pressure and diastolic murmur	New CRBBB	Intraoperative	Bentall
(9)	46, F	Behçet disease, NCC prolapse and LCC shortening	Acute heart failure	NA	NA	Bentall with infliximab and prednisolone
(10)	47, M	Intravenous drug abuse, IE	Lower back pain	Normal	NA	AVR
(11)	71, M	Immediately after MV surgery, iatrogenic aortic incompetence	Wide pulse pressure and acute pulmonary edema	NA	Preoperative	TAVI
(12)	53, F	Recurrent ovarian cancer and Trousseau’s syndrome, NBTE	Acute heart failure	NA	NA	Death
(13)	53, M	Dilation of Valsalva and ascending aorta, fibrous strand rupture	Acute dyspnea	NA	Preoperative	Bentall and ascending aortic replacement
(14)	70, M	After AVR and CABG, rupture of prosthetic AV leaflet	Shock and heart failure	ST-T wave abnormalities	Preoperative	TAVI with VA-ECMO
(15)	64, M	Bicuspid AV, rupture of anomalous cord	Dyspnea and diastolic murmur	NA	NA	AVR
(16)	95, F	Complicating PTAV	Shock	NA	Intraoperative	TAVI
(17)	80, M	Nontraumatic AV commissure avulsion	Dizziness and shortness of breath	Sinus tachycardia and CRBBB	NA	AVR
(18)	65, M	IE	Severe sepsis	NA	Preoperative	AVR
(19)	76, M	Fibrous strand rupture of LCC	Acute heart failure	left ventricular hypertrophy	Preoperative	AVR
(20)	55, M	Intimo-intimal intussusception-circumferential aortic dissection	Retrosternal pain and dyspnea	Normal	NA	Died while preparing for surgery
(21)	46, M	Type A dissection	Chest and back pain, Congestive heart failure	NA	Preoperative, MDCT	Replacement of ascending aorta
(22)	34, M	Aortic dissection confined to Valsalva	Heart failure	NA	Preoperative	Surgery
(23)	80, F	Type A dissection	Chest pain and diastolic murmur	Inferior and lateral wall myocardial infarction	NA	Death (refusal of surgery)
(24)	51, F	AV rupture (LCC) caused by valvular myxomatous transformation	Progressive dyspnea and early diastolic murmur	NA	Preoperative	AVR
(4)	57, M	NA	Acute pulmonary edema and syncope	NA	Preoperative	AVR
(25)	69, M	Local avulsion of AV commissure	Precordial pain, dyspnea and shock	NA	Preoperative	AVR
(26)	23, M	IE	Acute heart failure	NA	Preoperative	AVR, aortic root replacement Bentall
	59, M	Type A dissection	Chest and back pain, syncope	NA	Intraoperative, CT
(27)	67, F	Immediately after MVR, AV injury	Hemodynamically unstable	NA	NA	Another operation
(28)	63, M	Type A dissection	Chest pain and dyspnea	ST-segment depression and abnormal Q in leads I and II	NA, contrast enhanced ECG-gated MDCT	Ascending aorta replacement and AV repair
(29)	68, M	Type A dissection	Back pain	NA	Preoperative	Bentall
(30)	60, M	Spontaneous localized intimal tear of ascending aorta, flail NCC	Chest pain and subsequent shortness of breath	Normal	Preoperative	AVR

ECG: electrocardiogram, TEE: transesophageal echocardiography, M: male, AVR: aortic valve replacement, IE: infective endocarditis, NA: not available, CRBBB: complete right bundle branch block, F: female, NCC: non-coronary cusp, LCC: left coronary cusp, MV: mitral valve, TAVI: transcatheter aortic valve implantation, NBTE: non-bacterial thrombotic endocarditis, CABG: coronary artery bypass grafting, AV: aortic valve, VA-ECMO: veno-arterial extracorporeal membrane oxygenation, PTAV: percutaneous transluminal aortic valvuloplasty, MDCT: multidetector computed tomography, MVR: mitral valve replacement

Acute AR is an urgent condition, often with hemodynamic instability. If acute AR can be included in the differential diagnosis when subendocardial ischemia is detected on an ECG, it will lead to a prompt diagnosis and appropriate treatment. This case is a representative case with clinical implications. Furthermore, the findings suggest that not only coronary artery lesions but also proper control of blood pressure and the LV end-diastolic pressure are important for myocardial perfusion. This theory of myocardial oxygen supply-demand balance has academic significance in the management of severe heart failure.

The authors state that they have no Conflict of Interest (COI).

Supplementary Material

Bedside echocardiography on admission

Transthoracic echocardiography showed a normal LV systolic function with flaps in the LV outflow tract.