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Premature ventricular complexes are also referred to as premature ventricular beats, premature ventricular contractions or just ventricular beats/contractions/complexes. These terms will be used interchangeably in this discussion.

A premature ventricular complex is recognized on the ECG as an abnormal and wide QRS complex occurring earlier than expected in the cardiac cycle. It is caused by an impulse discharged from an ectopic focus which may be located anywhere in the ventricles. The ectopic impulse depolarizes the ventricles; because the impulse is discharged in the ventricles it will spread partly or entirely outside of the conduction system and thus produce a wide QRS complex (QRS duration ≥0.12 s). Refer to Figure 1 for an example.

The premature ventricular impulse replaces a sinus beat and induces a delay to the next sinus beat (the RR interval is increased after a premature ventricular complex). This yields more time to fill the ventricles with blood (increased ventricular filling). The person with premature beats might perceive this as palpitations, because of the stronger ventricular contractions caused by the increased filling.

Ventricular premature complexes are not preceded by P-waves, because the ectopic impulse originates in the ventricles and do not affect the atria (there are exceptions to this rule, discussed below).

Although premature ventricular contractions are mostly harmless, they may trigger sustained ventricular tachyarrhythmias. This will also be discussed later.

The impulse discharchged from en ectopic focus in the ventricles will spread abnormally (because the impulse did not enter the ventricles through the bundle of His). Abnormal depolarization will consequently lead to abnormal repolarization. This explains the secondary ST-T changes seen on premature ventricular complexes; the ST-T vector will be directed oppositely to the QRS vector. As seen in Figure 1 the premature ventricular complex displays a positive QRS complex followed by a negative ST-T segment. Thus, the ST-T segment is directed oppositely to the QRS (this is called discordant ST-T segment).

A premature ventricular contraction is followed by a complete compensatory pause which means that the next sinus beat will occur on schedule. The interval between the sinus beats occurring before and after the premature beat will be two sinus cycles (2 RR intervals). This is explained by the fact that the premature ventricular impulse does not discharge and reset the sinoatrial node, which will therefore continue on schedule. Refer to Figure 2.

When every other beat on the ECG is a premature ventricular complex (PVC), the rhythm is referred to as PVC in bigeminy (Figure 3). If every third beat is a PVC, it is referred to as PVC in trigeminy. Similarly there can be quadrigeminy and so on.

Two consecutive premature ventricular contractions are referred to as a pair or couplet. If 3 to 30 premature ventricular contractions occur consecutively, it is referred to as non-sustained ventricular tachycardia (if the rate is >100 beats/min) or ventricular rhythm (if the rate is <100 beats/min). If more than 30 consecutive beats are premature ventricular contractions it is referred to as sustained ventricular tachycardia if the rate is >100 beats/min.

Premature ventricular complexes discharged by the same ectopic focus will typically have similar morphology (appearance) and constant timing. Such premature ventricular complexes are referred to as monomorphic (or unifocal). This is exemplified in Figure 3.

Polymorphic premature ventricular complexes display constant timing but varying morphology. These beats typically originate in the same ectopic focus but the spread of the impulse (from that ectopic focus) varies from one beat to another (Figure 4).

Multifocal premature ventricular complexes have varying morphology and varying timing. These beats are discharged by several ectopic foci in the ventricles (Figure 5).

It is also possible to determine where the ectopic focus is located by assessing the morphology of the premature beat in lead V1. If the morphology in lead V1 is similar to a right bundle branch block (i.e predominantly positive), the ectopic focus is located in the left ventricles. If the morphology in lead V1 is similar to a left bundle branch block (i.e predominantly negative), the ectopic focus is located in the right ventricles.

If a normal atrial impulse is conducted to the ventricles approximately simultaneously as a premature ventricular impulse is discharged, the ventricles might be depolarized by both these impulses. This typically occurs if the premature ventricular impulse is discharged late, around the time of the normal sinus impulse. The morphology resulting QRS complex will resemble a combination (a fusion) of the normal beat and the PVC. Refer to Figure 6.

Although the complete compensatory pause is very typical of the premature ventricular complex (PVC), there are instances where it does not occur.

Premature ventricular contractions are common among both healthy individuals and there is robust evidence that do not affect long term cardiovascular prognosis among those individuals. Premature ventricular complexes are even more common among individuals with heart disease. Premature ventricular complexes can be debilitating, even for healthy individuals.

It is acceptable to have one or two dozens of premature ventricular contractions every day. Almost 30% of all healthy individuals display premature ventricular contractions during exercise stress testing. Male sex, stress, nervousness, tobacco, coffee, hypokalemia, infection, alcohol, sleep deprivation and certain drugs are associated with increased occurrence of premature ventricular beats. Moreover, the frequency of premature beats increase with age.

Healthy individuals might display premature ventricular complexes on ECG during screening. It may be symptomatic or asymptomatic. Palpitations and the feeling that the heart "skips a beat" are common symptoms. Chest or throat discomfort is less common.

A few premature ventricular contractions on a daily basis in otherwise healthy individuals is considered benign and has no effect on cardiovascular prognosis. However, if ventricular premature beats make up a significant proportion of all heart beats during the day, the situation is more problematic. If >15% of all beats are premature ventricular beats there is actually a risk of PVC-induced cardiomyopathy and left ventricular dysfunction. In such cases it is wise to refer to patient for invasive examination; it is often possible to eliminate the ectopic focus (foci) by means of ablation therapy. This can also reverse established cardiomyopathy.

Premature ventricular beats are common among those with heart disease. The frequency of premature beats is increased in a wide range of conditions, such as ischemic (coronary) heart disease. These individuals are generally more affected by the premature beats, as they already have compromised cardiac function. Because premature ventricular beats have ineffective ventricular contraction, it can reduce cardiac output and thus cause deterioration of ischemic heart disease and heart failure.

R-on-T phenomenon has been discussed here.

Underlying heart disease must be ruled out among persons without previously known heart disease. The procedure must be individualized and guided by ECG, anamnesis and findings from physical examination. Rather few otherwise healthy individuals necessitate treatment. Among those with heart disease, the proclivity to treat should be higher. Before treatment is instigated, it is important to analyse potassium and magnesium levels because hypokalemia and hypomagnesemia may cause PVCs and these causes are reversible.

Treatment is instigated if (1) symptoms are significant, (2) of PVCs make up a significant portion of all beats during the day (examined with Holter-ECG), or (3) if the PVCs have a negative hemodynamic effect. First choice of drug is beta-blockers (bisoprolol 5–10 mg once daily or sustained-release metoprolol 50–100 mg once daily). However, beta-blockers are often insufficient and symptoms may persist. Class I antiarrhythmic drugs can be tried, as can amiodarone. One should have invasive treatment with ablation in mind.

Normal Sinus Rhythm

Premature atrial contractions

Aberrant ventricular conduction (aberration, aberrancy)

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Director of Product Management Shiv Shankar noted that while the app is sorting and prioritizing these offers, the deals themselves come from your inbox, not from Yahoo.

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And by the way, if you’re a little leery of sending email from a Yahoo address, Jacobson pointed out that you can use the Yahoo Mail app to access non-Yahoo email accounts, including Gmail and Outlook.

The process of growing mangos from seed is actually pretty simple. While care should be taken during the extraction of the seed, both adults and children might find the process fun and worthwhile. Before you begin, make sure you have all your materials in place and ready to go.

The first step in the process is also the best: eat the mango! Before the large seed can be removed, the fruit's flesh should first be removed. Depending on the ripeness of the mango in hand, the rind can often be peeled off relatively easily; the bright orange flesh can either be sliced off with a knife or eaten somewhat like an apple. In either case, having some floss handy afterward is recommended.

After the husk has been thoroughly cleaned, let it dry for about 24 hours. Then, remove the seed from within the white outer husk. With the seed husk in hand, use scissors to cut a portion of the "thin side" of the husk. After an initial hole has been opened up, use the scissors to cut along the side of the husk to reveal the seed within. Be very careful during this stage, as the husk and seed can be slippery. The seed inside the husk should be white in color. Any brown or black coloration or patches usually means that the seed is no longer viable.

Remove the seed from the husk. You may potentially get more than one seed. Whether you see one or two depends on the variety. If you do see multiple seedlings, they can gently be separated and planted individually.

Wrap the seedling(s) in wet paper towels. One standard size wetted towel will be sufficient to wrap fully around an individual seedling to keep it from drying out. Once wrapped, put the seedling(s) in a zip-top plastic bag and keep in a warm, bright location until green growth begins to appear. Depending on the warmth of the location and maturity of the mango when it was picked, this waiting period can be anywhere from a few days to a couple of weeks. Be patient and avoid moving the bag around.

Once green growth has appeared, take the seedling out of the plastic bag and gently unwrap the paper towel. In your container filled with fresh potting mix, place seedling(s) at just enough depth to cover the majority of the seed without covering the new green growth. Keep your new plant's soil moist at all times and put it in a warm, sunny location. If you want to move your new mango plant outdoors, first give it a one-week period in dappled shade before placing it in full sun.

Mangos are full-sun (8+ hours of sun per day) in the tropics; these plants do best with lots of light, warmth, and humidity. If you live in parts of the southern United States like Florida or coastal Southern California where frosts are rare, you can plant your mango seedling directly outside. For the rest of the country, mangos can be grown indoors along a south-facing window. The addition of artificial lighting will be necessary in northern climates and areas that do not receive strong, full sun.

Otherwise, caring for your mango tree as a houseplant is as simple as growing other well-known indoor trees such as the common weeping fig. Give your mango plant a well-balanced fertilizer for the first few years of growth and then switch to a mix that's higher in phosphorus and potassium. A little goes a long way, so don't be tempted to add more than the package directions indicate. And only apply fertilizers during active growth in the spring and summer. Be sure to keep the soil moist for the first couple of years. Once the seedling has outgrown its first pot, transplant into a pot one size larger.

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