Listening to the heartbeat with ECG

The ECG machines are sporting state-of-the-art software that are keeping close tabs on COVID-19’s assault on the heart, allowing clinicians to react early and save lives.

From Wuhan, the initial epicenter of the coronavirus pandemic, a strong association was reported between preexisting heart ailments and how well patients fared when infected by COVID-19. Indeed, half of those who died had a cardiovascular condition, with hypertension (high blood pressure) being the most common finding (30%). As the epidemic moved from China and began to cross the globe, the reasons for this association were rapidly investigated yielding some interesting preliminary results. It seems not only do patients with a cardiovascular condition fare worse but they may be more susceptible to infection by COVID-19. Furthermore, there is stronger evidence that, after passing through the lungs, the virus ends up directly attacking the heart.

In addition to research as to how the virus damages the heart, clinical trials have also started to evaluate possible therapeutic answers. One example of this is the use of hydroxychloroquine or chloroquine administered in high doses with azithromycin. On April 24, 2020, the FDA issued a caution against use of these for COVID-19 outside of the hospital setting or a clinical trial due to risk of heart rhythm problems. Close supervision is strongly recommended.

There is strong evidence that patients suffering from COVID-19 are getting heart problems, whether it is a direct effect of the infection or of a systemic infection.

In this setting, the electrocardiogram (ECG) is one of the leading tools to assess the extent of cardiac involvement in COVID-19 patients and the effect of medications, due to its wide accessibility, low cost, and the possibility of remote evaluation. It is of great significance to study the changes of electrocardiogram in patients with COVID-19.

The pathology of the virus as it relates to the heart may not be 100 percent clear, but there is no doubt about its effects. As well as myocarditis, several COVID-19 patients in the study developed an irregular heartbeat, also called an arrhythmia. Researchers have also reported that COVID-19 posed a particular threat to patients with existing hypertension, because the virus appeared to block the hormones that regulate blood pressure.

Cardiac complications related to COVID-19 can be categorized into five types: cardiac injury (mainly due to ischemia or myocarditis); arrhythmia; new-onset or worsening of pre-existing heart failure; thromboembolic disease; and cardiac abnormalities induced by medical treatment.

One of the key readings on an ECG is the QT interval, which is an indication of the time it takes a heart to recharge between beats. The prolongation of that QT interval, also referred to as long QT, is a concern for clinicians, because it sets the stage for an abnormal and potentially fatal heart rhythm called torsades de pointes, or TdP—French for twisting of the points.

There are no hard and fast rules, but experts generally regard a prolongation in excess of 500 milliseconds (ms) as risky. COVID-19 can lead to long QT but—in an added complication for clinicians—so can the treatment of the virus itself: Several standard medications including anti-arrhythmics, antibiotics, and some anesthetics are also QT-prolonging drugs.

So are chloroquine and hydroxychloroquine, two drugs that have been discussed to have potential to treat coronavirus complications—but that are causing concern among scientists because of their possible impact on the heart. They might be cardiotoxic for some patients, which increases the chances of sudden cardiac death. If clinicians sense signs of trouble, they may need to urgently discontinue any QT-prolonging drug, adjust the patient’s electrolytes, administer magnesium sulfate, or even consider a temporary pacemaker.

That is why resting ECG machines have become important to clinicians treating COVID-19 patients. In particular, they are using state-of-the-art 12-lead machines, so called because they monitor 12 different sites of the body, which helps to build up a detailed picture of the heart’s electrical activity, including QT intervals. After administering any drug, they can continue to monitor patients with the machines.

Unfortunately, expert clinicians suspect that virus survivors who sustain cardiac damage might experience long-term effects after their infection has cleared—which suggests that hospitals will need ECG machines to help monitor COVID-19 patients long after the virus has retreated. But right now, that is a battle for tomorrow.

How complications may present when ECG is done
While ECG presentations vary, TCTMD has reported that cardiologists should be aware of any symptoms indicative of impending cardiac events, especially in tandem with other clinical indicators such as elevated troponin or lab work that could suggest acute inflammatory response, including high levels of C-reactive protein, interleukin-6, CD4, and CD8. As these developments emerge, they may warrant an ECG.

Generally, signs of complications may present on ECG in the following ways:
Arrhythmia manifests variably on ECG, dependent on the rhythm disorder, but it may be important to watch for signs of A-fib.

In one JAMA study that investigated cardiac injury among COVID-19 patients, all ECGs taken during biomarker elevation indicated abnormal heart activity, with researchers adding that the presentations aligned with myocardial ischemia. Notably, cardiologists may want to look for depression of the ST segment, depression, and inversion of the T wave, and Q waves. The study provided a supplement of ECG graphs from three patients (ages 73, 47, and 76) who demonstrated these changes.

Though research assessing the predictive value of ECG for sudden cardiac arrest is limited, previous studies have provided some insights. For example, one paper in the International Journal of Heart Rhythm discussed ECG presentations that could identify risk, including pathologic Q waves (as with prior scar tissue or myocardial infarction) and RSR’ patterns.

Because COVID-19 shares some symptoms with heart attack, there is an alert that there exists a possibility of MI going undiagnosed. Providers would do well to review essential patterns indicative of MI, including—as Healio outlines in a series of illustrative graphs—anterior/inferior/posterior STEMI and STEMI with right- and left-bundle branch blocks.

Cardiac monitoring is key
Given its newness and changing nature, the pandemic presents scientific limitations. As the science continues to develop and international practitioners share their findings and experiences, the data will undoubtedly change—as will recommendations for managing cardiac complications of COVID-19.

While this new evidence unfolds, cardiac monitoring will continue to play a key role in treatment planning. Be diligent, watch for changes in ECG, refer to advanced imaging when it is needed, and stay on high alert for abnormalities that could indicate problems.