麻豆果冻传媒影音

Why has an otherwise healthy woman in her late 60s had repeated episodes of fainting and dizziness for the past several weeks?

The woman presented to the emergency department immediately after one such episode, reported Mazen M. Kawji, MD, of OSF Cardiovascular Institute in Peoria, Illinois. Importantly, these spells occurred when the patient was inactive, she noted in .

The patient had not had any other cardiac symptoms such as heart palpitations, chest pain, or dyspnea. She was in excellent health and was not on any medications. Her family history did not include any similar symptoms, or sudden deaths.

Physical examination revealed no unusual findings and her vital signs were normal. Clinicians performed an ECG, which initially showed normal results; however, telemetry findings revealed premature ventricular contractions (PVCs).

A short time later, the telemeter recorded two episodes of fast polymorphic ventricular tachycardia (PVT) about 30 minutes apart. Each one lasted less than 4 seconds.

Clinicians ordered another ECG, which confirmed that the patient was experiencing PVCs. Findings of lab tests were all normal, including the patient's levels of serum potassium, magnesium, and three serial troponin levels. An echocardiogram revealed normal left ventricular systolic function, with no evidence of abnormal wall motion or valvular abnormalities.

Coronary angiography revealed a 50% stenosis of the patient's left circumflex artery. Instant wave-free ratio across the stenosis was 1.0.

The patient's PVT was determined to have been triggered by a short-coupled premature ventricular contraction that was identical in morphology and coupling interval to the PVC occurring a few beats earlier.

Patients whose hearts are structurally normal can develop PVT and ventricular fibrillation after experiencing PVCs with short-coupling intervals, which puts them at risk of developing syncope and sudden cardiac arrest, Kawji wrote.

Neither Brugada syndrome nor coronary spasm were possible causes of the patient's symptoms, Kawji noted -- the former because the patient's QT interval was normal, and the ECG did not show a coved ST-segment elevation in V1 through V2, and the latter because the runs of PVT were not preceded by ST-segment elevation. Thus, there was no need for provocative drug testing in this patient, Kawji explained.

Implantation of a defibrillator was necessary to lower the patient's risk of sudden cardiac death, Kawji said, adding that PVC ablation has potential value as a complementary treatment.

Following placement of a cardioverter/defibrillator, the patient was started on verapamil to suppress PVCs. While ablation was considered an option if arrhythmias recurred, the patient had only a single episode of nonsustained ventricular tachycardia about 3 months after her initial assessment, which passed without requiring a shock. No other episodes occurred during the following 5 years of follow-up.

Discussion

Kawji explained that the serial ECG findings showed "normal sinus rhythm with a normal axis, sinus arrhythmia, nonspecific P wave abnormality, and minor nonspecific T wave changes."

The PVCs were uniform and occurred frequently, he noted, with a right bundle branch block morphology and a right superior axis. The PVCs were followed by retrograde P waves. "The PVCs are superimposed on the T waves, most notably in lead aVF (the PVCs start after the peak of the T wave), consistent with the R-on-T phenomenon, with a short coupling interval of approximately 330 milliseconds," Kawji wrote.

The observation of malignant ventricular arrhythmias due to the R-on-T phenomenon was first reported in 1948, and again the following year, in a in whom R waves were noted on the T waves of antecedent complexes. Several of those patients died suddenly, Kawji noted. At around the same time, there were two additional cases of Adams-Stokes attacks related to ventricular fibrillation in patients whose heart function appeared to be normal.

PVCs -- which are -- are common in the general population, Kawji said, citing a in over 5,000 Framingham Heart Study participants with no clinically evident heart disease who were monitored for just 1 hour. Although the condition used to be viewed as benign in people with no evidence of structural heart disease, later data indicated that the condition carried twice the risk of cardiac death in patients with ventricular ectopy over 10 years.

In the 1971 system from 0 to 5, grade 1 corresponded to occasional, isolated PVC, while early PVC was graded as 5 to indicate the highest risk; however, the grading system was gauged to assess the risk after a heart attack, Kawji noted.

Kawji described the Lown and Wolf system grades 2-5 as follows:

• Grade 2: frequent PVCs
• Grade 3: multiform PVCs
• Grade 4(a): ventricular couplets
• Grade 4(b): >3 PVCs in a row
• Grade 5: early PVC (R-on-T PVC)

"High burden of PVCs and interpolated ones have been linked to cardiomyopathy in the absence of coronary artery disease," Kawji wrote.

The term "idiopathic ventricular fibrillation" describes arrhythmia in an otherwise normal heart and has been the cause of about 5% to 7% of cases of aborted cardiac arrest.

Short-coupled idiopathic ventricular fibrillation (SCIVF) describes premature ventricular contraction leading to PVT and fibrillation. showed that the mean PVC coupling interval was 293 milliseconds, and less than 300 milliseconds in 48 of the patients. Kawji noted that the patient described here reflects the fact that "the majority of PVC triggers of SCIVF originate from the Purkinje system."

Oral medications used in the long-term management of arrhythmias in the review of SCIVF patients included quinidine (83.3%) and verapamil (50%). Ablation of PVC trigger was attempted in 55.8%, and was successful in the acute phase in 83.3%.

Comment